I use two different tools, a plastic pie server and a Hackler honey punch. Any stiff plastic knife like utensil will work but one that is at least 6 inches long is best.
Even when when using nine frame spacing there will still be places on a high percentage of the frames that can not be cut off. They are either at the surface or just below the plastic comb, that's why I use the honey punch. The best size is the two inch roller and it works even better when you remove at least one of the spur wheels off the punch. Removing one of the spur wheels allows the wheels to spread and fall into the row of cells. There is no reason to heat the punch or rinse it off between frames. The hard plastic will make the wheels turn even when sticky wet with a buildup of honey and wax.
I also suggest that before you use the combs that you trim the tabs off the bottoms of the frames. It will make scraping the bottom of the frames much easier.