Re: looking for good instruction on loading boat on trailer
If trying to drive on when loading in a river or with a side wind, you need to approach the trailer at an angle. It is called crabbing because if you have ever seen a crab walk you know it walks at a sideways angle. What I mean is that to correct for the drift from the current, you angle the boat slightly into the current. The boat always stays on an imaginary line extending straight back from the trailer, but with the bow angled off a little for the drift. Not sure if that's clear, but I'll keep going. As the boat approaches the trailer, a few feet before it actually gets to the trailer, you then turn the boat toward the trailer to straighten it out. If you do it right, which just takes practice, the boat will glide up the bunks a bit. At this point, you can either bump the throttle a tiny bit to push it up enough that it is on enough that it can't drift off, or leave the engine idling in gear to keep the boat in place. Then wait a second to see if it is stable, hook up the strap and winch it up. Don't forget to shut the motor off and raise the outdrive. Loading and unloading on a river just takes practice and you will get it.
I know you don't have a roller trailer, but in my estimation, roller trailers are not for driving on, and are for walking the boat on using ropes and then winching it on. They work great for shallow water launches or where you have a dock right next to the ramp. I converted my roller trailer to bunks because the ramp I use most doesn't have docks alongside the ramp.