I would only use the above technique if you want 1" hair all over your hairpiece. thinning shears should be called blending shears as that is the only thing they are good for in my opinion. the above instructions will remove some bulk, but the hair coming out of the base will still be the exact same....therefore, its not really thinning anything out now is it?
Not if you want more scalp showing and less hair.
use the thinning shears for blending only. use them on the very ends of the hair shaft.
to effectively thin out a hairpiece, the hair must be pulled out from the base. so if you have a sfs piece, I would not recommend this as you can easily tear the base.
its best to order the appropriate density to begin with of course.
to answer the above question, yes you can use a razor comb, but if you are new to this, I HIGHLY recommend using the blending shears as you are much less likely to make a mistake.
DebbieS.