POD.

When I'm painting I move stuff from room to room as I go, or pile it in the middle and tarp it. You need to talk to your painter about what they need--presumably anything that will cause them to go slower will cost you more, then you need to pick your own trade-off between cost, hassle, and risk of spills. Never hired professionals for inside work, so don't know what the expectation is. Moving everything out sounds like a huge hassle, painting without anything in the way is much easier.

Ask the painters

Some people move the furniture into PODS or other on-site storage. You can get cardboard wardrobes from U-Haul.