Hi Steve, yes I've done it myself. It's very easy, all you do is paste some of the bleach on the hairs you want bleached, leave it for a while and come back. Once I did this just on the front hairs and it had a really nice effect on my front hairline... it was ultra subtle. In fact I was just experimenting, and just randomly placed some bleach on my front hairs.

Think of the bleach like styling gel - whatever parts of the hair you apply it to, those parts will be affected. In the case of gel, they will stiffen. In the case of bleach, they will just lighten gradually. And the longer you leave it, the more it will lighten.

Beware of some hairpieces though - some simply don't want to bleach. Example:
System 1 - Bleach it to totally blonde takes 45 minutes to 1 hour (I had to do this for knots).
System 2 - Bleach it to totally blonde takes about 6 or 8 hours

Total mystery, and nobody can explain that. Anybody want to try? perhaps some systems are treated somehow differently at the factory, or perhaps it depends on the donor? 6 to 8 hours is an awfully long time for the thing to bleach, and even then they aren't as bleached as the System 1 above.