Train with your shirt weekly It literally took me an entire year to get used to the groove of a denim shirt. Each shirt you use will have a different groove which will vary depending on how low you adjust the collar... By training with the shirt each week you will not only be able to handle heavier weights, you will also learn the groove of your shirt.
Strengthen your rotator cuffs to prevent injury Like most powerlifters, I often have at least one nagging pain somewhere. My right shoulder has bothered me for years. I know that the pain is coming from my rotator cuff, specifically my infraspinatus. In order to prevent further damage I perform internal and external shoulder rotation..
Work on proper technique every time you bench
Never perform a un-shirted bench max through a full range of motion If you compete with a shirt, then you need to train with it. Prove yourself in a meet, not to your buddies in the gym. I don't know how much I max raw and I don't care. Those aren't the conditions under which I compete.