BELZONA 1111 ( SUPER METAL ) is the best of all repair materials. I have used it on shafts from # 3 propeller shaft on USS Enterprise to blade carriers on 7 foot bush hogs. The secret to any good shaft/ spline job is surface preperation, surface preperation, surface preperation.
Molding techniques are done by first de greasing the part to be repaired. Surgical clean. Grit blast with angular abrasive for a 3 to 4 mil near white finish. Simply super clean the good part that you want to mirror. Be sure that all burs, and uneven linear wear zones are straitened or you will play hob getting the thing apart.
Put a even coat of release agent on the good part ( anyplace you don't want the BELZONA to stick) and allow to dry as per instructions. Properly mix the BELZONA 1111 until no color streaks exist, then apply a even and generous coat onto the damaged part. Assemble and lightly seat the two parts to get proper alignment. Wipe off excess material. Allow time to set. It is all about temperature and time. You can play with the temp to adjust the time. I always do a post cure with heat, just because that makes me feel better.
Seperate parts, dress down with files or grinder. Blind holes are no problem as this material has no solvents and cures from the inside out via chemical reaction. It is Nuclear Certified and well worth the cost.