The heel of your hand should never contact the forward assist on an AR. It is a forward "assist" not forward force. It is a thumb button only. If you have a dirty chamber, clean it. If you have an out of spec case, get rid of it. I have never allowed any of my AR's to get dirty enough to cause a stoppage. I can shoot 500 or more rounds w/o cleaning and have no probs.
For modern techniques, the FA is best used to lock the bolt closed after a chamber check.