Order of assembly? From a bare shell

Thanks Roy, I will remove the surface rust and spot prime those areas. I'm going to have to unpack parts that I've blasted and prepped to get a visual of what needs to go on prior to undercoat.
I would think the cavity wax could be done 1st for the frame rails and torque boxes etc.
Thanks!
Undercoating is thick and tends to be thick. I would think that should be the last thing to do after fuel line clips and brake lines are in and most all the other pieces like leaf spring hangers. Front fender guards. If you spray it first and you get it on any mounting surfaces, it's going to be a ***** removing that stuff.