Roof reseal

My trailer is getting some age on it and has never had any roof maintenance done so I think it is time to get it done. I had a vent start leaking on our last camping trip so I figured why not just do everything.

First question it what is the best way to remove all the old calk around all the vents and stuff.

second...about how many tubes of goop will I need. Its a 35 foot 5th wheel with single AC unit, 3 powered vents, sky light, and 3 plumbing vents. I hate to be short half way through the job but also hate to have a bunch of extra sitting around.

I also have the rubber roof paint. Should it be painted before calk or after.

Thanks for any help you can give a guy.