I once bought a Schwinn Heavy-Duti with chrome fenders. It appeared to have once been yellow, fenders nicely "misted" in rust.
I took Rustoleum's Rust Remover to it. 2/3 of the rust came off.
I took 0000 steel wool and WD40 to it. .332 of the rust came off.
I took chrome polish and 0000 steel wool, then chrome polish and a towel, then chrome polish and a t-shirt.

Then I buffed with a ShamWow. The fenders looked like new, other than dings. Heck, I even cleaned the undersides.

I did the same thing on the other pieces, like stem, bars, Ashtabula crank arms, etc. They all came very clean.

I tried the same thing on the paint, but stopped at steel wool and WD40, then washed and went to rubbing compound, then Kit Wax.

I paid $20 for the bike. It had original tires, original tubes. I had to buy a saddle, got one from a local junk store for $20.

It took about 12-14 hours of work, probably $15 of supplies.

I sold the bike for $160 plus shipping to a guy in Iowa.
A week later, he called for the fenders, $120 plus shipping.