1958 MGA Restoration 20b Tranny Tunnel Clean and Prep

De-gunkafying the transmission tunnel bits is done, though I have a long way to go before I'm able to start in on surgery so that they fit. Throughout my entire journey on this thing, I've been removing carpet nails from where a PO had used them for their intended purpose. Why nails and not glue, I know not ... This means that the whole thing is riddles with little tiny holes, all of which will mean water intrusion or rust in the future. I'm not sure how I'll fill them, but I don't want to weld them closed. I might use some kitchen or like sealant, smooth it all out, and paint over everything when it comes time. I intend to cover everything with carpet of course, so any hole plugging will be purely for gap closure, and not aesthetics.
I've taken everything to the local car wash to get the most of the junk and crap out, but there was a layer of grease that wouldn;t come off - I had to use a blow torch and a putty knife to get much of it out. I'm wondering if that was tar, installed by Abington, or just decades of oil that got baked and caked on over the years. I've also taken a flapper disk and a wire wheel to everything, to get rid of rust, junk, gunk, etc, and applied liberal amounts of etching fluid. That stuff eats rust and leaves behind a layer of zinc. After rinsing everything and letting them dry thoroughly, I've put down a layer of paint to keep it from flash rusting. In all, about 9 hours of work over two days.