First time cleaning enclosure how?

[Bogertophis]

Ok then I try to wait with feeding till he's shed.
How long will it be approximately? How can I tell how long it will take from now on. His colors are very dull now and have a grey hue to them, his eyes are already blue.

No way to tell you- snakes don't all take the same amount of time to shed, not even for the same snake at different times. It takes as long as it takes.

Good hydration & not being in the middle of digesting a meal will make it go faster & smoother.