I tried a couple different methods & decided on one method for customising my Candy Toy Medals:
Kujaku is the same as before: Dye removed from front design, lightly backsprayed metallic red, then backsprayed with silver, then the front textured areas were painted with a red wash. The overall color's a little uneven due to me not totally coating the back side with red, but I think this gives it a sort of fiery effect which I really like.
Unagi (technically Denki Unagi - what exactly is the difference?) was backsprayed with silver, then the front textured areas were painted with a blue wash.
Condor was done the same way as Unagi, but with a white backspray instead of silver (and obviously a red wash instead of blue, haha.) This is probably the most show-accurate method, but I think it also looks less impressive than the other two.
So, I'm settling on the Unagi method of a silver backspray & front color wash. I'd love to do all my Medals the same way I did Kujaku, but considering the fact that each Medal in a combo is a different shade of that group's color, I'd have to buy at least a dozen more cans of spray paint. I'll probably still do Taka & (my spare) Condor the more complicated way since it's Ankh's combo, but the simpler method will be just fine for the rest of my collection.