08/15 Booster cleaning question

[MrMilo]

After firing I let my booster soak in Ballistol for a few days and ran some hot water through it to get rid of corrosive ammo effect. I tried brushing it with my cleaning kit wire brush to get off the layer of fouling but I did not want to hurt the original finnish so I backed off of doing that. Here are a few pics please let me know what you think. I want it to be clean but do not want to do any damage.