Filing several test axles might be a good way to start. There are several other axle polishing compounds besides pumice and water. If you have access to a buffing wheel mounted on a bench motor, use can apply jewelers rouge on the buffing wheel and chuck the axle in a drill motor and apply to the buffing wheel. This is perhaps the best method. Dremel also makes a cotton buffing wheel that could be used.
Jewelers rouge is a commercial polishing compound.
I still have a little kit of several polishing compounds which I bought at Sears and Sawbuck about 30 years ago. Perhaps they still carry it. File down the edges of the chisel point on the axle . This should be obvious but perhaps is not. If you try to insert the stock Scout axles in the wheel without filing the edges, it may score the inside hub of the wheel.