Thanks. Hairing is my least favourite part of any bust! :lol
For this one I used a hot glue gun to lay down lines of glue (this seems the best option on resin for me as it has a very fast dry time). I tend to work from the hairline backwards (yeah, I know, pretty much the opposite of what should probably be done). Once the glue line is on, stick the end of a strip of hair onto it and press it down with your fingers (it doesn't tend to stick properly if you don't press it down firmly). This will of course get glue on your fingers, but if your hair layer is thick enough you shouldn't burn yourself. Anything that sticks out past where the glue line is (where it would grow from) can be trimmed with scissors and anything that hasn't stuck properly can be carefully pulled away.
After the first hair line is finished, the hair can be pushed away from the head, and subsequent lines of hair can be added, moving from the front of the head round to the back. Once everything is stuck, it will just need trimmed with scissors and cut to shape a bit.