Just $0.02. Depending on the active solvents(or not), any rubbber, dirt, oil or grease could render the tank of solution unuseable. We used to chromate alluminum, prior to painting, and every piece needed to be grease, dirt, and rubber free.
I will always advocate complete disassembly of flashlights before a chemical process, regardless of the material used to build it. Whether it's a $1000 Spy, or a $69 Four Sevens, they should be disassembled cleaned and prepped for the coating/coloring process.
GL