Rick, I suspect all the additional things are not necessary. I've applied the Home Depot "Henrys" brand elastomeric paint to my home roofs without using any "primer" or other additional materials and it lasted a good 5 years before I decided to recoat it. All I did in terms of preparation was to brush clean (with water) the roof beforehand. I've also used the same product on awning materials without any preparation. I don't really think any "base layer" is needed. I HAVE used the Kool Seal brand in small areas and don't really think it's any better than Henrys.
I suppose a product containing fiber might be a bit more durable, but what kind of stress is your trailer roof subject to? Mine is covered when not in use, so the roof is normally protected.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew