Thinning out crossing, rubbing, broken, etc. branches can be done at any time. SHOULD be done at any time! Rule of thumb for removal of a branch is to follow it back to the nearest OUTWARD growing branch or bud and make your cut there. If you follow that simple rule, your pruning will look natural, you will not leave any harmful stubs, and the tree will benefit.

Another rule of thumb: less is best! Your tree should not look like a herd of beavers have attacked it, but should simply look healthier!

Thanks rhizo for the info! I keep looking at those two trees and know they need the pruning but I am so afraid to tackle the job. It's not that I haven't done this before, but these two trees are just that..TREES. And the branches that need to be cut out are fairly large in size. Plus they just crisscross so many places I'm not sure any of it will help. It just looks as if they were left too long without shaping that it may be too late to help.
I am wondering that if I cut a branch that is one of the older ones, will it sprout from the bottom somewhere? I have a vague memory of one in my mother's yard that was hacked upon quite often by my father and it still always seemed to bounce back by sprouting new branches.
These are really a mess, growing not only into each other but into the fence.