My first attempt at metal work and panel welding

[Luv2exeler8]

Hey Guys, I'm going to attempt to replace my rotten metal myself and with the help of the occasional buddy who knows nothing also. I'm going to be putting in a one piece floor, inner/ outter rockers, cowl, header trunk pan, drop offs, inner/outter wheel wells and both full quarters. I want to fab up a jig on casters so I can stabalize and keep everything open to do the repairs. Do I just weld a jig up and have it supported on the rear frame rails and front two sub frame braces ? Also, I wanted to make a jig before I cut anything else out (my floor is the only thing gone as of now from the body - bolt on panels, doors etc..) to keep it square and help keep me from getting things out of whack. Any and all help with this process will be greatly appreciated for the fact this is my first build and is ALOT to take on I know. Also, as I replace the panels and strip the inside structure, what is the best thing to coat it with after I remove all the rust. I will be using a media blaster and also wondered what would be the best media to knock the rust. Thanks Guys !