I bought a Boss NS-2 Noise Suppressor at Sam Ash in Paramus over the weekend. That is a great store. The Guitar Center not so far away is also a good store. I often comparison shop at both, although the effect of internet retailing has been to make prices identical everywhere. This Boss stomp box goes for 100 bucks.
The NS-2 solves most (if not all) of my problems in amplifying my Dobro steel guitar.
How does a noise suppressor work? I'm just guessing from the tech descriptions in the manual. An algorithm searches the sound wave of the guitar signal, identifies the noise and cuts that noise from the wave. How that noise is defined... well, I don't know.
One of the nice features of this stomp box is the "Mute" setting. This turns off the signal to your amp. A great advantage for the Dobro, which accumulates feedback when I put it down within any reasonable distance of the amp. When I switch to using my Gibson on the second channel of my Fishman Loudbox amp, I can turn off the signal from my Dobro to the first channel.
Now that I've solved the worst of the feedback problems with the Dobro, I can work on getting the EQ right. I play mostly slide on the Dobro. When I bring the volume up to a rock type level, the surface noise of slide on string can be shrill and annoying. Most of that noise is in the treble range. I've ordered some strings designed for resonator guitars. I'll be trying them out to see what works best.