I personally won't be using a box cutter, a sharp razor blade sounds safer.
This year I will try a new method for growing tomatoes. We garden in two raised beds and crop rotation is difficult. We've been loosing plants early due to disease and replacing the soil is not an option for us. Extreme heat is also a problem and grafting can help with that.
Here is the Johnny's seed PDF on the process. It is a bit intimidating, but tomato seedlings are very resilient and I'm confident I can pull it off.
Of course I have to garden nerd this thing out, so I'll be growing non-grafted and grafted plants to compare the results.