Prepping, Rust Conversion, Sanding, ????

Im in the process redoing my engine bay.... Well after getting the engine out, I got a better look at the bay itself. I see from where the PO did his terrible paint job, there are "rough" spots. I can only guess that is surface rust... So I sanded a small area down and sure enough, the metal was good, but surface rust was present.

2 concerns I have - --1.. I dont want "rough" or bubbly paint when Im done 2...What is the proper way of cleaning the bay when you have some areas of bare metal exposed?

Im thinking if I pressure wash my bay down, and the bare spots get exposed, Im screwed??? Or do I just need to do something first? Should I primer the bare spots before pressure washing? Then resand off?

I'm going to go through all the trouble to sand my bad down, and I want to make sure it's going to be smooth. Should I use por-15 over a sanded bay or completly strip to bare metal?

Sorry for all the Q's just want it to be right.

NOTE: I just looked at eastwood rust encapsulator - Im thinking of brushing it on not spraying... What will I need to do after? I want a smooth finish? No brush strokes, do I sand smooth then primer and paint, or sand smooth and paint?

I was also just reading up on Por-15 --- Another site, said this...

Clean engine bay with pressure washer, then lightly sand all areas of the bay, sand more in "bad rust spots" to remove old bubbled rust. Paint on Por-15 (2 coates) then lightly sand till smooth and then seal & primer - then paint.

Does that sound about right?

One last question then It's off to get the RE... I only have "areas" of rust some parts are quite good. How does this stuff adhear without rust being present? If Im going to do my engine bay, I'd prefer to do the whole bay, not just sections.