I use Wipeout/Patchout with a jag and patches. I have boresnakes for all of my rifles, which I use to help dislodge occasional stubborn fouling. When I finish a shooting session at the range (or after a match), I run a wet patch down the bore and clean thoroughly when I get home. If there is heavy fouling, I will do an initial cleaning, wet the bore down again with a patch, and let it sit overnight. Final cleanup is normally pretty easy the next day.
In the case of my hunting rifles, I foul the bore while checking zero before hunting season begins. The rifle isn't cleaned again until after hunting season.
How often a given rifle should be cleaned is highly dependent on what kind of ammo you are shooting, barrel quality, and barrel condition. Environmental factors may also come into play as well. I don't believe in cleaning intervals based on a set round count.
I generally clean if one of the following conditions is met:
1. The rifle tells me to clean it (indicated by a drop off in accuracy).
2. I am testing loads with different bullets and powders. In that case, I clean the rifle before switching to the next bullet/powder combination and foul the bore with the new combination before testing is resumed.
3. At the end of a shooting session, match, or hunting season.