Any NVDS will work, but the key is to get the solvent under the gum spot. Most guys just flood the carpet with solvent, and that may be the quickest method when you have to deal with vast quantities of gum, but some carpets or installations don't take well to that. (If you're working with fewer spots use a marinade injector to squirt just a little solvent under each spot instead.)
We customized an old tool so that the vacuum slot would be perpendicular to the carpet in use, then aimed a jet toward the slot with about a two-inch gap between them. The hot water gets under the edge of the gum spot, peels it off the carpet and shoots it right into the vacuum slot. Slower than solvent but safer for some installations.
Our experience with gum grinders made us wary of using them on anything but carpet that couldn't be hurt by their aggressive agitation.