There is nothing to worry about. The best thing that you can do after the surgery with your grafts is to leave them alone and wash them thoroughly. Don't squeeze the pimples as you can make matters worst by infection leading bigger pimples and a bigger mess.
A baseball cap will not damage the grafts as long as it doesn't press too much against them. But by week 4 the grafts should be already â€œfusedâ€ with the scalp. Try not to rub the cap against your grafts. I'd rather go with a bandana or â€œbeanie hatâ€.
Also, Aspirin really helps against skin redness, but I don't know if you are supposed to take aspirin 4 weeks post op.