Traditionally barbers use larger shears with a straight handle or ergonomic handle. This is what I have used for the majority of my career. As of 2 or 3 years ago the side of my thumb was starting to get really sore where the barber shears would rub when I cut hair. This has been a problem on and off throughout my career due the amount of the scissor over comb technique I use every day.
A few years ago I switched to using swivel thumb barber shears. For me they have been a career saver. The swiveling thumb has allowed me to slightly change the angle of the thumb hole and that part of the barber shear now rests on the back part of my thumb. I have no more pain or soreness regardless of how much of the scissor over comb technique I use. I would highly recommend any barber having similar issues with pain or soreness to give these type of shears a try. They come in all different sizes depending on your comfort level. I recommend a shorter one for picking up hair and cutting over your fingers and a longer one for the barber shear over comb technique. They may feel a little awkward at first but it only took me about a week to get used to them. Now I feel like have been using them my whole career.