Sure, I'll clarify.
1. Make an instrument rack.
2. Drag your VST into the rack and turn it off.
3. Duplicate the VST; one copy for each preset. At this point if you open the chain selector they should all be at 0.
4. Go into MIDI map mode and select the VST on/off button. Map it to a TOGGLE button with the value from 64-127.
I have a LaunchPad, so in my case I've programmed it to show a grid of 64 toggle buttons. Toggle means press it once to turn on, press it again to turn off. Each button in the grid corresponds to a VST, so if I want to play the first preset I press the first pad. The pad lights up to show me that the preset is selected/on. To turn off the preset I hit the pad again, and it goes dark.
My controller doesn't turn off all other presets when I select a new one - that would probably require some heavy scripting. When I change patches I do have to turn off the old one before I turn on the new one. It only takes about 1/4 of a second but I agree it's not perfect. With the LaunchPad I can see which patches are on so I don't have to worry about accidental layering.
I've organized my patches in rows by type (piano, mallet, string, pad, lead, bass, etc), and since there are only 8 per row it's easy enough for me to remember what's what. 64 sounds is a lot, and it's enough to carry me through a set. It's a good memory exercise, like "Go Fish." That said it would be easy enough to map a button on the LaunchPad to send the channel to my headphones so I could audition my instrument selection before it goes live.
An IDEAL situation would be a rotary control with an LCD screen that showed your current preset, but that would take some deep programming and even then you'd have to remember which preset names sounded like what. I haven't used this with CPU or RAM-intensive VSTs or effects because I don't own any, so I'd be interested to see how this works with something big. Is that what you meant when you referred to audio effects lurching as they buffer?