WOW!! Your work is always top notch. Silver soldering is an art in itself. Not sure a resistance iron will work with the brass frame being so much thicker than the cross bracing. Torch is going to be just as challenging due to the size difference. Some sort of heat sinks or the heat blocking putty may be your best bet.
Took me awhile to get the hang of soldering on my Studebaker. The grill alone took over a hour to solder together and I made a jig first. Glad I only have to do about 8 or 9 more solder joints and it will be back to machining again.
Would really like to see your work in person. Course I would probably just stare and drool over it.
I do a lot of that at the NAMES show each year.