Good luck, Nathan. Last time I cleaned my block I removed the water pump, poured CLR in there until it almost poured out through the water pump hole and left it for a couple of days. Then with a straightened coat hanger with a little L bent at the bottom I worked to loosen all the junk in there (it will be the worst at the back cylinder which is not easy to reach), left it another day and drained/neutralized it, discarded that stuff at the city's waste place and repeated this procedure. Once that was done it cooled better and has run pretty clean. I don't own a power washer, so I can't speak about that, but Joe's suggestion might be good. I also used some cleaner made by Prestone. I may as well have run some orange marmalade in there for any good that stuff did.
