Hi Ray I think I'd stay clear of pressure washing....you could wind up digging out the grain and end up with deeply ridged shakes that will look a bit tacky. Although I haven't done it, I watched a paint contractor strip the paint off a cedar shake house using a propane torch with a special diffuser that kept the flame quite low but emitted lots of directional heat. Now, I know, you're worried this will burn the house down, and I half expected that to happen....but with this torch and a stiff wire brush, he was able to strip off many years of paint quite easily....and ne're even a dark scortch mark!! A good subsequent scrubbing with a bristle brush and TSP and a good dry period and the house primed out well with an oil primer and painted beautifully with a semigloss latex (2 coats).
Might want to check with a local paint store that caters to pro painters.