I counsel frequent breathing breaks. And (assuming you can) leaving the bathroom window open overnight.

We've got the window open, and we'll run a fan tonight. And we both have lead-paint-rated respirators.

Unfortunately, for many many years people have painted this bathroom without removing the paint underneath. So we've got truly amazing amounts of paint to remove before we can even start putting more paint on. I've been cursing them, of course, but I must admit that painting without stripping is starting to sound a lot more appealing.