Yes, you need two snare machines; one that has your normal snare and another that will do the ghost hit snares.
Your normal snares go on 5 and 13, and your ghost snare hits surround those and would do something like 3,4,6,7 and 11,12,14,15. Of course, adjust to your taste.
Now on your ghost snare track, set up a random LFO to control the volume. Trigger type would be HOLD and because of this, the speed really shouldn't matter, though I would make it something off-tempo, say 11.
You'll need to play with your ghost snare track volume and then also the depth of the LFO to get the right feeling.
Good luck!