Proper Preservation Techniques For Copper Coins

The oil prevents air getting to the surface of the copper coin.
Museums often use pH neutral oil to prevent air getting to ancient copper / bronze / orichalcum coins. Renwax is also one of the products often used by European museums for this purpose.
The coins sit in display trays exposed to the air, without a Mylar film covering them.

Actually, the patina they have acquired over the centuries helps to protect the metal underneath. Applies to early American copper as well.

Cleaning the soft brush with hair shampoo OK, because hair shampoo is pH balanced neutral with a buffering agent.

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Bright oange mint freah looking bronze and copper coins are highly valued. The best that you can do with these is keep them in airtight screw capsules. Generally speaking, slabbing does not provide this level of protection from air.

Dessicant and clip lock polyethylene bags, in assistance with airtight screw encapsulation, would keep the fanactics quiet. Unfortunately, not much of a way to display beautiful coins.

Blue ribbon from the video is no longer sold. One of the ingredients is now banned. What is recommended now?

The TPGs use bare hands as well, I believe.

I don't know ; I'm not likeing hitting those coins with a brush . I'll stick to the Verdi-Care application .