I am not a loading expert, but It really helps to have two people working together.
The characteristics of the ramp also seem to make a big difference. A ramp out of level or shallow / steep may take different strategies.
I am not a fan of power loading but it really helps me with my bunk trailer. I back the trailer just far enough to slowly load the front toons partially up the bunks (and hook the strap). This seems to hold the front of the pontoon centered. Then we back the trailer in another 3 to 4 feet, depending on the water level, while trying not to float off the trailer(the front is still centered and somewhat anchored).
All the bunks are wet before loading and my bunk trailer has the plastic covering (no carpet).
Lastly, if the rear of the pontoon has moved out of alignment, due to wind or waves, I can crank the motor and adjust with just a little power to swing the back and over.
I have had my share of strange trailering over the last 30 years. Sometimes it was so out of alignment (especially in my non-pontoon years with a roller trailer) that I would back in the water and try to adjust. Not always fun if the ramp is crowded.
I also try to load during off peak times but recognize that may not be possible at some ramps.