I also have a full size truck with a cap, for the washing and clay parts of the detail opening the doors will help you reach on top. You will probably be detailing the interior following the exterior so a little water inside will not hurt anything. For any machine work I would recommend a 4 ft. Step ladder so that you do not have to worry about tipping it over on the paint. If you work in 6 sections, moving the ladder for each section you will easily be able to reach all the roof areas. Also for the front of the roof, flip the mirrors in so you can have a little more room to play with. You may also want to lay a towel on the roof next to your work area so you can keep all of your chemicals right next to you and not have to keep walking back and forth to pick something up. It can also act as a place to lay your machine down when not using it. And one other thing, take a beach towel and wrap it around the top of the step ladder then tape it with some duct tape, this is good for a just in case precaution. I hope this helps, I've been doing this for a few years and it has worked very nicely for me.