It's a good idea. It certainly doesn't hurt. After all, the bench presser has to work less immediately before an attempt. In a competition, any aid (such as a bench shirt) is welcome. (If you are doing a heavy single bench press at home, please always have either a spotter or two or do them in a power rack with properly set safety bars.)
Straighten up your back and shoulders first of all, And than you unrack it and take a couple steps back keep your feet at shoulder width or slighty wider. Take a deep breath and go down like your about to sit down to make a 90 degree angle with your legs. (DO NOT LOOK UP, This can damage your neck just look straight while you go down). While you go down to a 90 degree angle explode back up.