I'm going to agree with the folks above but also reiterate just practice with it. Finding neighbors with old horses has helped me! (Sorry for my dark sense of humor there!) I've spent lots of time digging up honeysuckle, removing dirt/mud from my pond, landscape work (really helps you get better with both ends of the machine, and I agree with whomever and the loader side being trickier to manage), digging up tree roots, etc., but I'm way less experienced than a lot of people here.
I dig with the extendahoe out when needed (though my manual suggests extending all the way and retracting a few inches), it's not a problem and what it's there for, though I do try to keep my swinging side to side to clean/flatten stuff to a minimum, extended. If the dirt is soft and light you still won't have any trouble but when you try to push side to side on big rocks or heavy piles that's when you can mess stuff up, as I understand it. Rereading your post though I think you are saying using the extension to pull your bucket back and forth? Yeah, I don't do that with the bucket engaged in dirt. It's too slow anyway, extend, dig, dump, repeat, unextend as soon as you don't need to be extended.
Figuring out where to place the machine is tricky as well, compared to the hole you are digging. Remember that you will always be cutting a big V in front of you (unless you have one of those hoes that slides side to side), so keep that in mind. You'll need to move over a bit to make square holes. I tend to put the hoe side of the machine probably about 2-3 feet from where I expect the hole to stop, digging towards myself, but there is a sweet spot. Usually, the biggest issue I have there is there hoe doesn't get low enough close enough to the machine to dig. There is probably some genius that can do the math so you could pull up to a spot and dig exactly where you want but that ain't me.
I'm reading above and when I hear "flat bottom bucket" I usually take that to mean, on my bucket at least, the part just below the teeth, where the bucket is straight. It's amazing, if you go dig in your garden and leave it lumpy, how well you can come by and move pretty huge amounts of material to fill in empty space, and it's quite satisfying to do it well! Watch out for your bucket not pushing material or getting hung up on stuff because, again as I understand it, this is a good way to start ovaling pins and bushings and adding lots of slop to the works.
I think I mentioned this elsewhere but in case you didn't see it, go get stuck somewhere, or pretend you are stuck somewhere. At some point you will venture into a wet or soft spot and start getting into trouble. You can learn to maneuver around without having to flip your seat and drive to a new spot. All this involves using the hoe as; a crutch to pick up the big tires and slide them side to side, or an arm to drag or push yourself. At first it's pretty scary.
Almost every time I dig with the hoe my loader bucket is in the ground to help anchor the machine and the stabilizers are down. In that position you dig like you want to then to get unstuck or to move a bit you'll want to raise your loader bucket and stabilizers a bit, maybe 6-8 inches, boom/stick in some (I think I'm usually about halfway depending on the situation), curl your bucket so you can put pressure on it going straight through the metal rather than flexing it a bunch (like using the teeth) and SLOWLY boom down with the bucket straight ahead of you. I repeat, it'll be scary. You'll feel the entire machine lift up like
@NH575E avatar picture (except his has the loader bucket down too, making it difficult to move) and likely rock a bit. From there SLOWLY boom sideways and you'll feel and see the machine pivot. You can also use the hoe to drag/push yourself around (just make sure the e-brake is off!) which is much faster and easier than switching to the driver's position. Once you get comfy lifting/moving the hoe side of the machine with the hoe you can unstick from a lot and move yourself around your holes pretty easily.
I've been belly deep, literally sitting on the pan, in very soft, wet mud next to the creek and had to extract myself from the mess. It took a fair amount of lifting to get my tires back on top, then a fair amount of dragging myself away from the pit I made. It was my first go at getting unstuck and it probably took me an hour and a half of white knuckling. Take a break and a breath! Go slow! Wear your seatbelt!
The last horse I buried I got good and stuck as my tires just filled with mud, 4x4 wasn't helping and I realized quickly that it wasn't getting better (knowing this is very helpful!). In that kind of situation I had the space to boom and stick out as far as I could, bucket uncurled, then used the curl and a bit of boom up to drag myself back to more solid ground. Again, for the love of Christmas, go slow. There is a trick to doing this and it's really easy to be a couple feet up in the air before you know it. You'll feel the machine tipping like crazy and feeling quite unstable (stabilizers just a few inches off the ground!) and that's when you slowly boom in to lower the cab. When you've got it right you are curling and booming in at a nice slow tempo together and you feel the joy of the wheels rolling toward the hoe. You often will want the bucket pretty deep in the ground to get good purchase and hopefully it's not also too wet or soft but don't be surprised if you end up digging a hole there too to drag yourself out of something. There really is something magical about pulling yourself free! Also remember that when the situation looks dire you can use a comealong attached to your bucket and a healthy tree or something solid as the support to pull yourself out. I've never had to go that route and you want to be dang sure you don't pull the tree down onto yourself, making that a less desirable method.
Lots of words! Have fun! Burn some diesel! Go play around! I also watched some backhoe olympics which helped me learn the capabilities of the machine and found that what I was doing wasn't far into the realm of what hydraulic power can handle. Granted, I try to keep my machine relatively planted but they can manage a lot!