I have been a auto painter for a while now and I agree Imron is probably not a good paint for DIYers. Very toxic and not user friendly. Most any 2K urethane paints are also toxic and require an air fed hooded respirator to spray safely. Before I use house paint, If the siding was in decent shape. I would wash it really well with a strong degreaser and a red 3M scotch pad. I would then paint it with rustoleum thinned by directions.
I have painted a lot of things with rustoleum and it has held up surprisingly well through the years. Better than what most RV manufacturers are using these days. The only big drawback is drying time. I'm not talking spray bombing but purchasing the gallon cans, thinning and spraying with automotive spray gun.
Good quality automotive paint and primers are very expensive and desired results will vary with the painter's skill level. Not worth it to me on a common travel trailer that will see a lot of use.