+1 to JimmyHAD

I believe it is the same with everyone, that the chin area has the TOUGHEST whiskers.

Do what Jimmy said, curl your lip over your lower teeth and use your other hand (pointer and thumb) and stretch the skin to either side. Sometimes I have to dry the sides I already shaved to get a good stretch going, so don't be afraid to try that too.

I never go ATG on the chin. I would just get razor burn. I find that 1, MAYBE 2 passes XTG gets my chin BBS. It's kinda weird, my chin is probably the easiest spot to get BBS Not sure why that is...hehe.

*EDIT* And my razors did that even when they are sharp enough. So that's not the reason