On my 1929 Westfield, which had about 7 layers of black paint over everything, and other layers of paint under it, then the Berkshire Blue, I used a lot of things.
I used easy off, nothing.
Lacquer thinner, right through to the metal.
Goof Off, just wouldn't get through the black paint, whereas the lacquer thinner would, aggressively.
Acetone, well it got a minuscule amount of the black, but I figured it would take about 2 years of non stop work.
Finally, I used Kleen Strip aerosol paint remover, 3 to 5 minutes then immediate bath to remove everything possible.
Ultimately, I had to stop at this step, as now, anything takes it down to the bare metal, and I am happy enough to have enough original paint showing, along with the red highlights old Raymond Buck painted on it sometime in the last 90 years when he had it. As his name is stamped into the stem, I blame him, may he rest in peace. I am still not happy with him, for painting over the bike so many times.
So, until such time as it comes to repainting it, if ever, this is how it will be. I now have 6 coats of carnuba wax on it, and will continue to keep it coated with a high quality wax as long as I have it. Unless I decide to have it painted back to the original scheme by my daughters boss, who does supreme paint work on antique vehicles.
I am kind of fond of the red, white and blue look for now.