Either welding process should work. Brass may wear down quicker and put you back to square one......snip........ I'll look into the Bijur systems. Do you have any suggested suppliers?
I do have a question regarding building up the shaft. Since it is steel, would it be better to weld it (MIG) or braze it?
Just thought of something, go buy a piece of 11/16" hex stock locally or from Speedy Metals, and just remake the shaft. Much easier and cheaper!
As for the Bijur lubricating stuff, there's lots of stuff on eBay for sale. In fact, there's a place out on the west coast that sell a Asian brand that is used on Acer mills. He advertises on eBay as Supra Machine Tool, I think. Easy to find his stuff. He may have a kit made up of all of the stuff needed to convert a knee mill over to automatic lubrication. Be prepared to spend upward around $300 for the necessary stuff to convert you mill.
When you get to that point, let me know and I'll try to put together a lube diagram of all of the points of lubrication needed with a basic list of items for a shopping list to look for.