Cupping your hand around a pneumatic port and blowing into your hand has almost "0" chance of hurting instruments.
Putting your mouth (or worse, a compressed air gun) against any port may either hurt instruments, blow a line off, split the side of a line or more.

I can't see any normal glider speed/pressure, due to speed, hurting anything......unless you consider the US space shuttle in the same group. That will go a wee bit faster than most of us are used to.
;-)

Granted, a "cupped hand puff" only shows air moves, it does NOT show minor leaks. We did that in the spring once, everything moved correctly, I did first spring flight.
At about 100', the ASI was really low, basically no ram air instruments for the rest of the flight (ASW-20).
I did manage to do some miles and a few hours without the panel working.