Jamie, this is a pretty easy thing to do. You can use the prop screw in doing it ,but I don't recommend it as you can easily bend the screw. It can be done if you hit the screw with a swift square hit with a small hammer. I place the crankcase on a flat surface with the prop driver facing up. I then place a allen screw(5-40) in the threaded hole and tap with a hammer. The drive washer is a press fit with splines on the shaft. The crankshaft will drop right against the surface you  placed it on. When you reinstall it, its a must to line up the splines. I then made a tool which is a large nut which fits directly against the drive washer and it has a hole right through the middle of it for the prop screw. I use a small adjustable to hold the nut side while using an allen wrench to tighten the prop screw . This not only assures you that its on all the way, but it puts the drive washer on squarely. This is the most important part. You will know instantly if the splines aren't lined up. The next few things I list are some neat little tips to make these engines work a bit better. I do a bit of crankshaft polishing when the crank is out. If you have a drill press, you can use 800 grit paper and a bit of oil and polish the shaft . I then work my way through some finer grits up to 2000 followed with a bit of polish. Its not necessary but it does make the engine turn up nicely. You can dress the back of the case with fine paper on a flat surface such as a piece of glass as well. This removes and high spots and flattens the surface for the gasket.  I polish the inside of the crankcase where the crank rides in as well. I found that castor gets really varnished on the surfaces on the crank and case which acts as a brake when you try and run them. Inside the case there is an oil groove that is cut into the case. I make sure that it is clear an xacto knife can work well here. I found that you can push the baked on varnish right out of the groove with the tip of the knife sometimes. One thing to note, if you use a polish inside of the crankcase its a must to clean it out thoroughly. Abrasives can become left in the case which will then work as a lapping compound if you run it like that. I use pipe cleaners and other nylon bristle brushes with soap and water to clean it out. Ken

In lieu of the hammering, you can accomplish this with less wiolence buy pressing the shaft out with a vice or a big C-clamp.  Either way, put a 5/40 allen head cap screw in a substitute props bolt.

Having recently dismantled a similar engine, I would recommend NOT pounding on it.  A small gear puller, perhaps filed or ground to suit the small size, works the best, and safest.  In any case, apply heat with your $Kote heat gun to the drive washer to expand it.

Floyd

Crankshaft removal tool:

http://coxengines.ca/product.php?productid=292&cat=11&page=3

Assembly tool:

http://coxengines.ca/product.php?productid=62&cat=11&page=3