Technical Sealing metal, undercoating after sandblasting questions

I'm getting the body on my Fleetline project stripped soon (using mobile Dustless system with rust inhibitor) and it will need the bottom sealed up afterwards. I've replaced floor sections and done a few small spot repairs so I'll need to seam seal those areas as well.

First question- Since I'll have a fresh bare metal surface should I apply the undercoating directly to the bare metal or or should I spray a epoxy sealer over the whole body- top, bottom, inside and out, before anything else?

Second question- should I apply seam sealer prior to applying undercoating product?

And last question- is undercoating the right product or should I use POR-15 or something similar ?

I'm trying to build this car to last; it is going to be a driver not a show car so durability is my goal.

 

I would spray it all with epoxy before anything else.

 

Epoxy then seam sealer, I prefer the two part seam sealer....

 

Self etching primer. No rust ever(almost))

 

Spray a runny epoxy primer that will seep into all the nooks, crannies, and folds of the metal. I'd paint it with a topcoat next, personally. Then scuff for undercoat adhesion. I'd guess your undercoating should take the place of any seam sealer and bridge small gaps and pinholes

 

Self etch primers are not for sandblasted surfaces, epoxy is.

 

Use epoxy primer over clean white blasted metal , and you will have the best grip for plastic , primer , paint , known !!!