Yes a dowel or bar, that has some clearance on the spindle bore, makes putting on and taking chucks off very easy in deed. And they are nicer to handle with a little bar each side as well. Especially the heavier 8 inch or so chucks. I have some 5/8 ali bar for the Myford chucks, and some 25mm ali bar for the import lathe.
It greatly reduces the chance of dropping or having a chuck slip as well.
The best part is that the threads for the Myford are already quite close to alignment when putting the chuck on. I feel that long term it looks after the spindle threads and has to help the chuck/backplate threads as well.
Neil