If your painting your whole room (not just patching uP), I'd deeply suggest moving the tank out of the room.
If you wouldn't sleep in your room right after its been painted, why should your fish? It'll take atleast a full24 hours for the paint to dry, and the fumes go away, if even that short of time.
You need to move those fish outta' there, but if your afriad its going to be too much work, go ahead and risk it.
At one time or another, if you use the blanket Idea, your going to need to remove the blanket to check on them.