transfection of cells while in arrest

Hi,
I am interested in transfecting a human cell line (U20s or MCF7) that is arrested at G1,S,and G2.
have you ever done this successfully?
how did you arrest the cells?
how did you transfect?
what was your efficiency compared to normally growing cells.
I am grateful for your time, this is crucial for my project,
Noam Diamant.