This is tough to explain/describe. Much easier in person... but here goes nuthin'...
When you look at a branch from above, there should be the central branch going down the middle, and side branches. The side branches should alternate, left, right, left, right... sometimes, there's both a left and a right. One of those is a canidate for removal. There's usually larger side branches and smaller ones. The larger ones should be closer to the trunk. If there's heavier branches out near the end, you might want to prune them. Sometimes in addition to the major side branches, there's small branches mixed in, coming off the main central leader. Maybe they're weaker than the others. These are good candidates for thinning. If they don't have a bright green growing tip, they're not strong. You can eliminate them.
Once you've "cleaned up" the central leader, then do the same for each secondary branch. Then the tertiaries, and do on. Eliminate the old, dead and weak foliage.
Go thru the entire tree like that.
Don't pinch off any bright green tips. Instead use sharp scissors to cut entire little tufts off at the base of their stems.
I don't have a Procumbens to use as an illustration, maybe Brian Van Fleet does.