I doubt I would ever do something like this with steel. Building up aluminum is no big deal, but on steel sheet metal I would always weld on a fitting or maybe even braze it on, depending. Then the fitting could even be brass. By the time you got any steel built up the sheet metal would no doubt be warped pretty good, possibly overheated, and the weld might be pretty tough to drill and tap. Annealing would fix that part but it just seems like way too much on the con side for so little on the pro side. Now if you want to build an aluminum tank, then you might go that way.

Most conduit fittings I've seen are die cast and not the best material for TIG welding. Lots of impurities. They are also usually threaded NPS, same thread form and pitch but no taper. You can screw tapered fittings into them, and it will usually work, but not the best match. I always keep my eyes open for things that can be repurposed from other industries. Why reinvent the wheel.

The only reason I did this the way I did was that the sides were tapered and I needed the fitting to be straight. At first I actually made a little tapered fitting to weld on, but I wanted all the welding on the outside, and with the lip on the pan it was just too tight to get in there and weld all around. So I just built up the boss from weld metal, since that was an easy option.