Thanks for the compliments. Actually you are some of the first to see some of these.
As far as working with steel, it's not that different than working with brass. A little harder to cut, bend and roll. Machining takes a bit more patience as you need to take lighter cuts using cutting oil. That gets pretty messy.
Most of these were built before I got the lathe and milling machine. You don't need fancy equipment to build a locomotive. (but they are fun to play with) The atlantic was the only one using them. tha boiler was a peice of black pipe turned on the lathe, cutting the areas between the boiler straps and the smokebox, then laminated the smokebox with apeice of embossed beercan. I cut the othe end and spread it open to form the firebox. The other boilers were rolled sheet steel and soldered, which I would recommend doing, it's actually a lot easier.
The drivers on the atlantic have mini-ballbearings from VCRs on the axles. Speaking of the drivers, what do you think of those thread spools.
I would be glad to share my secrets to to keep this so called "dying breed" of scratch building alive. I wouldn't know where to start. So please ask, hope I can help.
An HO steel E6