I use the pad of my finger on most of my guns... A hold over from my 1911 time.
Only gun that still gives me problems is my USPc - I keep shooting low w/ it. Haven't figured it out yet. Of course, when ya have several guns, 1 of them has to be the one you shoot the worst. I spend most of my time shooting my P99, so I needa spend more time w/ it.