Maybe this is unconventional, but I usually siphon as much as possible from kettle to the primary fermenter, leaving behind about 20% with all of the sludge (hops + break material). I will then take this remaining 20% and pour it through a 5gal nylon strainer bag, swishing it around to get as much liquid through as possible, and then I squeeze the remainder out by hand. This captures most, if not all, of the hops and a good portion of the trub stays in the bag as well. I don't like wasting wort, and it doesn't seem to matter if some trub goes through the bag. I DO like to get all of the hops out of there, so this method works well for me.
As far as filtering at any other point, it's a no-no due to airation of the wort. Airation is desirable during transfer from kettle to primary, so filtering is okay at that point.