One other thing that may help is to (if possible) approach the trailer from slightly down-wind/current. The slight angle uphill will give you a bit better control over the bow of the boat until you hit the bunks or rollers, when some self-centering should start to take over. Then correct your angle to the trailer with the steering, apply power to seat the boat on the trailer, and use bursts of power to get it as far up the trailer as you desire.
Note that I've pretty much given up on this, as I'm usually diving, so don't mind getting wet recovering the boat. I hand-walk it onto the trailer and wade in to do the winch strap and winching.
And, no, I don't think I've ever seen anyone who gets motoring on right each and every time. And sometimes it's really ugly, too...