I have recently heard a Baal Tokea before blowing the Shofar during Elul, blow air into the Shofar without making a sound, (I have seen something similar some years ago). Is that necessary or even recommended?

Poskim don’t mention such a minhag, but if the Baal Tokea feels his Shofar may needs the blowing for cleaning, it can be done before the public compliance of the mitzva. Horav Shlomo Miller’s Shlit’a opinion is that it should be avoided, since it may be considered as an added voice of the Shofar.