Is there a blade steel you prefer or a HRC above which you would prefer for your own skiving blades? I'm thinking about buying either a CPM 20CV (59 HRC) or CPM 4V (63 HRC) blanks, have them heat treated and made into a flat tip or diagonal tip (English style). They both are tough and have good edge retention. 20CV I have some experience with, and it's easy to sharpen. 4V? I have no clue, but its toughness would probably require some extra work. The blanks available are 1/8" thick, a little thicker than I would prefer but the only maker using 1/16" thick 20CV that I know of has a minimum 20-week wait.
Do you have any recommendations as to the angle of bevel, the shape of the blade, double bevel or single, the width of the blade? Also, what's your thought on these knives? https://www.peacheytools.com
I think the best way to go about it without spending a bunch of cash would be to use what you have already, a belt sander as you mention can already be a huge help. If you want to do it all by hand then you'll need a good file and a jig to help you with angle of the blade.
Here is a nice video of a easy DIY angle setup for hand filing:
https://www.youtube.com/watch?v=r9iNDRwwBQQ
I would get it as close as you dare before heat treatment, since there is always a chance of deformation. At least that's my limited understanding of how to go about it.