I tried your advice on two lenses, today. ETR 50 and 150mm. I did the 150, first. The interesting thing in that one was that there was no sign of any lubrication whatsoever. The shutter was definitely not firing correctly, though. I brushed lighter fluid onto the area you suggest and it came away with nothing. I think the mechanism may have always been dry, since it differed significantly from the 50mm, which obviously had lubrication. On the 150, if you fired the shutter 10 times, it most often opened with a significant lag. It seems to be working properly, now. The 50 - the shutter wouldn't open half the time. Now it too seems to be working properly.
I'll check them again in a few days. They'll probably still be fine. I didn't squirt lighter fluid in there and I only used machine oil on a toothpick to lightly oil the mechanism - and then actually brushed it to get some back off. Last thing I want is oil on the aperture or shutter blades (although I don't know if it can migrate from there to the shutter mechanism).
And - thanks. The 50mm makes the Bronica so much more interesting.
Do you know if the same sorts of problems with RB67 lenses can be solved in a similar way?