Wipe one direction only. Do not overlap or scrub back and forth with LMF browning solution, or you will get "coppering".
Good advise..
and if you do miss a sliver of surface you can catch that on the next cycle.
Going back over an already coated surface with the stuff just causes problems.
Don't warm the part either,,that will deffinetly cause the copper sulfate in the LMF soln to plate out the copper.
Sometimes the copper plating will dissappear as you continue . Othertimes it seems to spoil the final appearance.
The latter moreso when using the process in Rust Bluing than in Rust Browning.
The tincan with some water in it on the wood stove is good for humidity.
The part hung above it is good but you need to capture the humidity as it rises off the stove around your part(s).
If you can hang a cardboard box above the stove/water can with the bottom being open & the part hanging free inside of it..this 'tent' will capture the warm humid air you need to create the fine controlled rust on the surface.
Be safe if you do this,, a wood stove and cardboard box are not the best of pals when in close proximity..
The rust coating does not have to be particularly heavy. Just a slight brown thin covering.
Sometimes it takes a second coating of the soln to get things going,,usually not on plain low carbon steel though.
CArd the piece with a wire wheel (carding Wheel), steel wool (de-oiled), etc.
Some people re-coat the surface with more LMF soln.,,for Rust Brown I find that there is still soln on the surface and active
so I just rehang the part(s) and they re-rust again,,,and again..etc.
If Rust-Bluing, they are re-coated as the boiling water cycle kills the rusting action of the chemical and recoating is necessary to get the next rusting.
Sometimes LMF resists ceasing to rust becasue of the Nitric Acid in it.
A batch in a strong Base like Sodium Bi-carb sometimes helps. I find Sodium CArbonate better (Washing Soda). Be very careful with it as it is nearly as strong as Lye. ..Lye soln in water is another strong alkali soln.
Oil generally does not stop acids from being acid. But a long repeated rub down will eventually get you there. But usually the After-Rust will have created a more matted finish by then.
Not necessarily a bad thing if that's what you are after. But if you want to halt the stuff at the last carding, then you need something to neutralize the acid content of the LMF.
Not continualy adding more coats of the soln each cycle and letting the first coating do the entire job helps keep the After Rust down as well.
If you have a Shower/Bathroom that you can use as a DampRoom as explained already,,it works wonders for creating the rusting cycles.
I've done it this way for probably 40yrs winter & summer, mostly for Rust Bluing. Takes about 1 1/2 to 2 hrs to get a rust coating.