How to seal welded areas that not accessible

[ken4444]

To avoid rust, what are the proper techniques to paint or seal the back or undersides of welded body areas that are not easy to reach?

Would it be best to spray a weldable primer on these areas before welding, then try to spray epoxy primer on them after welding?

In the past I used a weldable primer (maybe from Eastwood) that came with a 24" long plastic tube that could be snaked into difficult to reach areas, but since you can't see what you're spraying, it's a crap shoot. I ended up with paint dripping out of holes and running down the exterior metal in some places.

Maybe I have answered my own question, but I have to believe there may be better solutions, or maybe techniques that are specific to specific models of vehicles. I'm curious what a professional would do.