A padded 2' pipe wrench will work as a compressor wrench. Also, if you have a jig saw , 0r similar saw, you can make a field expedient pulley wrench from a chunk of plywood. Liberally douse the pulley threads with penetrating oil a bit before starting.
Loosen the two 9/16" bolts, hold the compressor side of the pulley with a big wrench or really large slip-joint pliers and turn the outer sheave clockwise a half turn or so. Then make sure the engine stop is pulled out and bump the starter to free the belt you just tightened the pulley down on. If you tighten it too much at one go you risk crushing a spot on the belt.
Repeat until you get the correct tension and tighten everything back up.
Lance