I have converted an older single plate stove and cast Iron pan into a solder bath.
It is working quite well but I need some advice on the method. I am finding that the layer of solder is quite thick, I basically lightly sand the tracks, coat with flux paste then dip it into the molten solder. The results differ all time.
Are you trying to duplicate the solder plating used on commercially fabricated boards?
That process is called hot air solder leveling (HASL) and is accomplished by dipping the board in molted solder, and then lifting it out as hot air from air knives blows off most of the solder.
I think (I may be wrong), but many years ago the solder was applied and the excess solder was removed by running a roller over the surface of the board.
EDIT:
I just googled "roller tinned pcb" and got lots of sensible hits.
I was not a figment of my imagination after all!
What I did once or twice was to heat the board in "peanut oil" in a pan suspended somewhat. I'd pluck the board out. Add some solder and smear with a damp rag and do it again. I probably would not use the method for stuff that is concerned about leakage currents.
Where I used to work, we evaporated Nickel. Nickel never soldered well in my opinion. HP used to use a process of Copper/Nickel/Gold. The Nickel is commonly used as an underlayment to get the gold to stick.
The little soldering to Nickel I did, used pure Indium which is a very low melting point metal.