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I'm halfway through something - have done the masking with the fluid but haven't time to finish the painting. You can also get it in a fibre-tip pen which draws ok on bike paint in my case, but I guess also steel. It's called a molotow (https://shop.molotow.com/en/marker-refills/molotow-grafx-art-masking-liquid-pen-2mm.html). It dries pale blue when the pen is working smoothly but a bit clear when less comes out.
I have experience with masking fluid on watercolours. I think it will stick to steel just fine. It feels a lot like tubeless tyre sealant actually and dries up to a rubbery film that you can roll or peel of afterwards.