You talkin' with a gun?
In my experience, bleach almost always changes the color or the shirt a bit when just used in one small place. You'd also have to contend with the degradation of the fibers.
Do you now have the time to get some proper spot fluid?
I know that with plastisol, some use acetone (but very flammable)
I've also read on forums that brake cleaner in a spray can has worked , but I don't see it as I always figured the pressure of the gun was a great part of the operation.