How do you grab a girls breast?

you can but you have to say all the right things all at the right times and then you just turn her on by you are so sexy then touch and there you go (she might let you have sex
One at a time is about the only way. Actually, take your time and you can fondle one girl while suckling on the other and go back and forth until the inevitable happens, which is the girls will get tired of this.
Unless you are her boyfriend. If not, dream on! I don't know.. she could let you if she lets you or she really likes or loves you.