A slow cooker generally doesn't boil - or certainly not quickly! Takes them 1-2 hours to reach a 'simmer' which I would guess is 70-80 degrees? The cheaper the slow cooker likely the lower quality the heating element/pot so they take even longer - or don't get that hot. Many of them have a 'High' setting, which does boil (100 degrees) but can take 2+ hours to get there, but I am talking meals, so really 1-2L of fluid compared to what you're heating for the wax. Most of them will not tell you how hot they get. I've no idea the thermal properties needed for the wax - nor how you would get the corresponding details for an off the shelf slow cooker.
We've got 2, a
Crock-Pot and a bigger
Morphy Richards - the MR definately get hotter faster and reaches a higher temperature, even with it being bigger than the other. Makes much nicer meals for things which need the higher temperatures (like pasta bake) compared to the other, so we only tend to use that for currys and things which take longer.
Sigma, but will always shop around as they're not the cheapest for many things...
Did you ever do the bath thing when stripping components? Pretty sure it wasn't a slow cooker, sonic bath/Sonic cleaner thing? Something like that.