Well, if there is a problem even with careful use of a blowing bulb,
there is too much dust/grit to allow safe polishing of the lenses. That leaves rinsing as the safer alternative.
That means to carry along a squeeze bottle filled with water to squirt over the lenses and then blot them dry. No polishing, no rubbing and hopefully no more lens damage.
PS
Licking the lens clean may not be practicable in a very dusty environment.
