Metal prep and primer questions

I am in the process of restoring a 1950 Ford 8-N tractor that was my Dad’s (bought new the year I was born) I am comfortable with all the mechanical aspects of restoring the tractor (I have already rebuilt an engine for a 9-N) but the painting part is confusing to me.
I have been reading many of the forums about priming and painting the tractor but I am still a little confused. I would like some feedback on the plan I outline below to see if I missed anything or am making myself a headache later when I finish paint the tractor.
I will be cleaning using various methods, electrolysis, sandblasting, wire wheel etc. As I rebuild parts (hydraulic top cover, steering box etc,) I would like to clean them, then treat with Picklex-20 or Must for Rust (MFR) and then when I have enough to make it worthwhile to prime the pre-cleaned pretreated parts all at one time.

This is where my confusion starts:
#1. I have cleaned parts with electrolysis but there is still some black stuff left in the pits of the metal does this black stuff need to be gone or can I apply Picklex-20 or Must For Rust over it.

#2 I have seen some discussions about Picklex-20 and MFR, if I use it should I scotch bright parts again before I prime or can I prime over it without a problem later on.

#3 I will wipe everything down with some sort of surface cleaner (any recommendations).I plan on using an epoxy primer and plan on 2 coats within the recoat window. Can I then apply a surfacing primer over that in the recoat window and then do all the final color coat at a later date. Will that need to be scotch bright before the final coat?
#4 Most of the above in regarding the cast iron parts that I will be dealing with first. Can the same basic procedure be used on the sheet metal?

Any recommendations on surface cleaners,paint brands for the epoxy, surfacing primer, sandable primer, and finish coats would be appreciated.
This is something I have been wanting to do for many years and I want to do as much of the work as I can.

Thanks in advance for any answers or opinions on my plan. Sorry if it is long winded or has been covered before, I just want to make sure I understand the process.

#1. You should try to remove as much of the black oxide as possible, but for trace amounts as you describe it will be fine. You can apply Picklex 20 over it with no problem. If it will be sometime before you prime, then you need to keep it in a dry environment.

#2. When applying Picklex 20 all that needs to be removed is residue from runs etc. There is no need to scuff, put I would use a good wax/grease remover such as PPG's DX330 to remove any contaminants that may have settled on the piece.

#3. Wipe down with the DX330. You can use a surface primer over the epoxy within the window and then later top coat, just make sure you have the epoxy covered fully. Since you say this applies to cast parts, there is no need of using a surfacer unless you are looking to smooth out the cast. Surfacer primers are used on sheet metal to cover in minor imperfections and give you a good smooth surface for your top coat. They come in different build capabilities.

As for scuffing the surfacer before top coating, generally you would want to sand it with 320 or so to remove any nibs or other imperfections and create a bonding surface for the top coat. (speaking of sheet metal surfaces) If you use the surfacer on the cast parts,it would also help to scuff the cast too.

You can prime with epoxy and then wait for the top coat, but you'll have to scuff the epoxy, reprime and then top coat.

#4. The same procedure can be used for the sheet metal. Again, you must decide if you want to use a surfacer primer on the cast parts. For smooth sheet metal a surfacer works very well.

Many recommendations can be made as to paint, the real question is how full is your wallet and how much money do you want to part with. If you are looking for a good midline epoxy, you'll find PPG's Omni brand is often recommended. Surfacer and top coat in the same line can be purchased. Do you want to use and acrylic enamel or acrylic urethane? The urethane will hold up better. Surfacer is a sandable primer. Hope this helps.

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Thanks for your reply good to know I am on the right track. I will continue to read forums I know I still have a lot to learn about painting