“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
I use the dr.t film cutter as well. When I asked the same question (for the same reason) I got the "use scissors and patience" response as well. Labs use a cutter, why shouldn't I. Less errors, especially with frames that are close together on curly film.
Look for Fiskars shears (with mightily sharp needle points) and do the cut over a bright lightbox. Steady, confident hands will do it. Of course less of a margin for stuff ups when cutting 35mm than 120.
Fiskars can be bought from hobby shops that have stuff for sewing. I have had mine for more than 15 years.
Lab operators are not necessarily deadly accurate, as witnesseth a lab chopping through the last frame of a roll of 120 film! I had plenty to say (none of it repeatable here). I've never cut through or ruined any of my own trannies. Just my fingers...