Think of it as encouragement, not cheer leading. Its simply a way of acknowledging… “I see that you can smell a truffle and it is difficult to locate. You are doing great. Take your time.”
I will often simply say “You can do it. Keep looking.” For dogs who are sensitive to pressure, I will start to look around in the area WITH them. This takes direct pressure off of the dog and helps them relax a bit because you are both looking for the same thing.
The other reason noting this behavior is important is because you will later see a different change in behavior that will mean “there are no truffles here”. You will understand all of these subtleties before heading into the forest.