I run slime as needed. Works great, I tore a big hole in my one of my rear stockers, patched it from the inside and slimed it and had no problems with it. I just put on new 27" Swamp Fox Plus's and had an issue with the rear tire going flat over night. Tried new stems, new rim, re-cleaning/seating of the bead and rim to no avail. Put in a bottle of slime and no issues.
Does make a hell of a mess, when it comes to changing the tires, so I prefer to keep nothing but air if I can help it.