i do this a lot. assuming you have already done some research and watched a couple of videos on how to wrap a perm, here's a few additional tips to optimize the process for toupees.
-the hair needs to be in good condition (for a wig). the better the condition, the better the perm will take and the more defined the curls will look. if the hair is really frazzled to begin with you won't get more than a soft curl and the perm will only frazzle it even more.
-make sure the formula you use is safe to use on high-lift tinted/bleached hair. my favorite is Zotos Quantum Platinum but it was discontinued recently. maybe you can still find it. the only ones i know about that are still on the market are Texture EFX Color Treated (I found it a bit harsh) and Joico K-Pak Waves Color Treated (not tried yet).
- pre-cut. if you blunt cut the hair on your piece to an even length beforehand, it will be much easier to wrap. that can make for a tighter wrap and firmer curl. i'm just talking about cutting the ends, you shouldn't cut it into the style you're going to wear until afterwards.
-use pins to secure the rods to a foam head, that way you will get the curls to form as close as possible to the roots/base. i like flower head pins for this.
-the longer the 'creep time' (the time between rinsing out the waving lotion and applying the neutralizer), the more defined your curls will be. the hair used for wigs is very porous, simply towel blotting it and applying the neutralizer right away per the box instructions will not suffice. Wait *at least* several hours until the hair closest to the rods is bone dry, or overnight, or ideally 24 hours before putting the neutralizer on...
-... in fact, you don't even need to bother with the neutralizer. if you leave the rods in for a couple of days to oxidize after rinsing the waving lotion out, it will have the same effect. that's the old fashioned way of neutralizing a perm, the chemical neutralizer just speeds it up so customers don't have to endure the discomfort of wearing the rods on their head overnight. Since you're not wearing the rods on your own head, why subject the hair to more harsh chemicals?
i'm not very active on this board anymore but if you search my posts here and on the NWL board you'll prob find more info about DIY perming.