That may be a cabbage maggot, also called a root maggot. Most other pests stick to eating the leaves and stems of radishes rather than going after the root.
It will work but you have to be very careful not to accidentally sand the sides of the pitcher with the sand paper as it will show extremely visible scratches....
Start with garden-fresh radishes, not those rushed to mature in the retail market. If you need to keep them in the fridge, take off the stems as far as you...
The safest is what the video recommends. The basic rule of thumb is that you know when you're getting close to the blood supply or the quick when you see...