Whatever i do i seem to get some wrinkles in the back of my piece. I usually attach both sides at the same time and was thinking maybe i should stick down one side first and then the other? can anyone offer any advice on how to avoid getting such wrinkles? thanks for any help

Ok do it like this :

1) Attach the front 2"-3"

2) Attach centre

3) Apply glue to whats left at the back and allow to dry then pull piece slightly and press to scalp.

Do it in the 3 steps above.