to do a really good all over bare metal bird is very simple.
Prime with Stylnrez grey or white.
Use AK Xtreme metal Aluminium directly on to the primer. A white primer will keep the aluminium at the natural shade level that you see in the bottle, Grey will darken it a little.
Leave to cure and dry properly for a day. You can touch it within a few minutes if you need to, but I would just leave it.
once cured, apply a coat of AK Gauzy shine enhancer. This will protect the paint . Contrary to popular belief and this is from my own experience. The paint does NOT like being masked, this is why I always put a coat of the Gauzy Agent shine on and leave that for a day too. Never rush these things. You have time!
Once the protective coat has dried you are OK to add stencil masks, insignia and also group colours, markings etc. Decals will go onto the Gauzy agent shine enhancer too as it acts like a gloss base.
Usually the paint used on insignia, group colours, markings etc would be a matt one, so once on, those need a protective MATT coat over the top.
You will get very good at masking building this bird.
That's the best way of producing a B-17G with a natural aluminium shine.
Of course, there were G variants with the Olive Drab colour for this you need Vallejo Model Air 71.316 N. 41 Dark Olive Drab and 71.298 M495 Light Gray.
The Mask sets I have posted are very good and I usually use them whenever I can. The Eduard canopy masks are really a must. they are all ready to go and do the job first time without messing!
It may be extra expense, but with the Maketar sets you not only save a lot of time, but you can get more than one aircraft out of a set of national insignia so they pay their way more than once!
I would like to follow your progress, so I hope you post on here with pics!
James