I do the same as below: Back in to wet the bunks, pull ahead so top of fenders are above waterline. Back boat off of dock and drive boat ahead to get a little momentum at idle speed and slide up bunks until it "sticks", jump out and winch it up the rest of the way.
I personally don't consider this powerloading. To me, powerloading is driving the boat on until it contacts the trailer then giving it throttle to push it up to the winch post - similar to what Bugle Trout described. I have seen guys go to 1/2 to 3/4 throttle wiht the engine trimmed up. To me this is where the launch damage is done. I see this quite often on lower Green Bay, there are no signs that forbid powerloading..... yet.