With the wussy little slide lock button found on Glocks if your thumb is preventing it from locking back on the last shot then clearly you're pressing in too much with your thumbs.
For shooting semi auto pistols the last part of our thumbs are simply useless appendages. The usual two thumbs forward grip style is just to find an out of the way parking spot for them. If you're pressing in to the the side hard enough to hold up the slide lock you're pressing too hard.
To be honest, I find my thumbs very useful for manipulating the thumb safety on my semi auto 1911. Maybe that's just me




















































