[wvguy]

You are on the right track. Pressure wash but of course don't get yourself in trouble with the lead. You don't need a moisture meter. No one has one and average consumer don't need one. Instead sounds like there will be plenty of work to do after you pressure wash for the wood to dry. Just make sure of two things before you prime. First, remove all loose paint and second remove all loose paint. Then prime with such a old house I would use a oil based whole house primer. I say whole house because most are only spot prime outside. Second topcoat with Latex top coat something that is 100% acrylic latex is ideal. Just make sure you work on one side of the house at a time and don't wait long after you prime before you paint. Never more than 2weeks maximum before topcoating or else your primer could fail.

Hope this helps.