I have been in the situation where I have been taking pictures for a virtual tour in an unfurnished house that is painted pretty much beige from ceiling to floor. Of course my digital camera can’t auto focus on a blank wall under these circumstances and manual focus is a crapshoot.
What I have found that works is to take a leaf rake along with me. Put the rake against the wall with the tines facing up and in the center of the area of focus for the camera lens. Fortunately, a leaf rake is just about perfect height for this. I let the camera auto focus on the rake tines and then switch it to manual from there to freeze the focus. Remove the rake and take your shot. Rake-N-Take works every time with no fuzzy pictures!
1st Choice Realty, Keowee Key