I flush mine with a water-alcohol solution usually in the 3.5% - 7% range pretty much on a daily basis.
I've got to try that!!
Roughly every other keg, I'll run oxiclean/pbw through the lines. I was doing the first cleaning of 8 retired soda kegs yesterday, so was running a lot of oxiclean through the lines when I was pressure testing the rebuilt kegs.
Atomic Dog Brewery
On Deck: Imperial Stout, Nut Brown
P: American IPA, Irish Red, Barley Wine, Smoked Porter
S: British IPA, Hefe Weizen, Zinfandel
K: Apfelwein x 2, Graff, Phat Tyre, Lefse Blonde, Cream Ale
T: 3 Hearted, Dry Irish Stout