Tran, after an overlong nap, I took the decision to keep the chamber on my machine all white, for the same reason you did. I'll leave the upper as is and I've already given the lower its first coat of Titanium White, which is brighter. I did not sand but used a wooden 'probe' to scourer all the loosened paint free of the wall and simply laid the TW over what remained. This paint is very heavily pigmented and as heat is used to set acrylic paint, should be fine in this application.
An interesting note about this enlarger is the previous user had taped a light yellow gel over the diffuser panel. It was not very obvious to me when I first examined the thing, perhaps because I was so focused on the peeling paint, but that changed quickly enough when I removed the pane for painting.
I wonder if I should return this filter with the diffuser and if I do, what will it affect, especially when using VC filters? Any thoughts?
One last thing; this enlarger has a large 'dish' turret of VC filters, about 9 of them. Has anyone here used one of these before and if so, where the heck do I mount it?
Cheers