I am trying to finish up welding the roof on my cab. I cut it off just below the drip rail across the back panel. I have a cheap HP mig welder & its taking forever to weld it in. The welder makes a mess and is hard to get a good bead, so it had a lot of small pin holes. Rather that keep re-welding & grinding, I was going to paint it with POR-15 and then do my plastic filler work over that to smooth out the area. Since POR-15 is supposed to encapsulate the metal I thought I would use that to prevent rust through & bubbling the filler later down the road. Any Ideas on this????