Check with Fleetwood, we have an old 92 American Eagle, ours required the primer as it was an alpha roof.
You need to make sure its clean. We scrubbed and scrubbed ours then took everything off it and let it dry good. But our skylights were old and brittle.
We put the primer on first and let it dry for a few days.
When you get ready to put the primer on put plastic down the sides you do not want to get it on the sides and tape it down good, leave it on for the final coat. On the liquid roof one thick coat is better so it says then multiple coats. We started real early one morning and it took us till almost dark, it was a l o n g day for sure. Ours is 38 foot.
You want to make sure the original is attached well, if not it would not attach either. Ours was getting flaky but still attached well, by scrubbing it we took off oxidation and excess flakiness. Read how to patch any holes in the rubber roof if you have any. Glue any loose spots down also. I cleaned off all the thick caulking around the old skylights I took it off with a heat gun. I'm not sure if you want to do all that but will give a more professional look.
Seems like we paid $700 for the coating but bought more then we needed as we were afraid we would not have enough. Also we bought it online, if you buy a can and don't open they don't take it back directly. there is a way but talk to the supplier, something to do with fed regs, don't remember now but not easy. My husband used a squeegee to spread it and I used a brush around the curve as we moved down the roof and I made sure there were no runs. It will even out as it sets up and fill indentations you can still tell where they were but they will fill in. We let it dry several days, also we did all this work undercover. it says it can immediately take water but we had openings all over the top where all the items had been removed. Also we found it set up quicker then they said it would, likely to do with the heat and humidity. Hubby worked his tail off getting it done in one day.
Attached is a picture of the finished roof, we think it came out good. Preparation is the key to a good outcome. This was done in the summer of 2012, still looks good but its in a garage most of the time.