I don’t do mine too often (but then it is nearly always used in relatively clean, dry conditions). I use a little tech wash with lukewarm water, in the bath, let it soak for a bit and agitate it every 15 mins or so for an hour. Drain the bath and let it dry there, again move it about every few hours to aid drying.
In my experience you need a strong solvent to get the dirt out and something just a little corrosive to make it nice and shiny. Soak in a 1:1 mixture of battery acid and petrol for 20 mins. Then neutralize it with some thing alkaline like Mr Muscle sink un-blocker. The a quick rinse and your good to go.
P.S I’m sorry please don’t ever do any of the above.