The best advice I can give without being present to demonstrate is to let the knife do the work and essentially just slide the edge of the blade across what you’re trying to cut while only allowing the weight of the blade itself to apply the downward force until the edge catches. You should never really apply much downward force to cut in general so that the knife can actually slice instead of essentially wedging what you’re cutting apart. The hardest part is getting the blade to catch at first so it might take some finesse to start a cut but other than that there isn’t much else to it. Obviously there is a point that a blade is essentially unusable if it is completely blunt but in most cases a dull knife can get the job done. One last trick, for tomatoes and other soft things with a tough skin, using the point of the knife to slightly puncture the skin first will give you a place for the dull edge to catch to start a slice.

It’s all about the slice. One of the best lessons I ever learned in the culinary field is being able to cut with a dull knife

Coooking is about knowing the secret to success. It’s not the secret ingredient it’s the secret knowledge to do the task the best way. If the knife is sharp it should be done a certain way and if the circumstances are different then it should be done differently. But if you want to know how to do something the best way in a specific situation, the question shouldn’t be about the tool specifically but rather the technique for the situation considering the variables. I can tell you how to cut things with a dull knit but if the knife is sharp, my advice would be different