The 1.1s are untipped. If you're going to rework nibs to a CI or even your own stubs, the better way to go around it would have been to start from a stock Broad nib.
Getting a round point from a stub is possible, but in this case of starting from a Jowo 1.1, non-optimal. For one thing, it's bare steel at the tipping. For another, while the stub has the horizontal width to work with, it doesn't have the vertical height to result in a properly done Broad. A Japanese F or M might be possible. The understanding required is no different from getting a round point from anything else; tools used, while important, are secondary.
I use a dremel for all my nibwork.