Don't mask them off. Just stop spraying the finish. Then wet sand the edge.
Forget masking the shaft. Assuming you spray more than one coat, spray your first coat 8" up the shaft, your second coat 6" up the shaft and your third coat 4" up the shaft (or something along those lines).
When dry/cured you'll find that most of the "feathering" work is already done for you.
TW