My CCW's are (in order) a Glock 23, Glock 26, Keltec P32, and a Kimber CDP 5".
I use a 50/50 mix of ATF and STP. I use a generous amount on the rails. It tends to stay put, but excess will leak out/down. I use CLP to clean my barrel and the last patch I put through the barrel is a little wet. I completely coat the outside of my barrel. I don't leave oil in the barrel, but I don't pull a dry patch through either.
Chances are a little oil in the barrel won't do much. Alot of oil, like filling a .40 or .357sig barrel and immediately shooting will cause the barrel to swell and ruin the gun. But I doubt it would do much more.
Generally I over lube. Never had problems with collecting grit. Then again, oiled grit is better than dry grit. I shot at the range once a month and then clean my CCW. Otherwise it stays cocked with one in it's pipe, and in it's holster 24/7 until my next range trip.