These Berman Airways, are they something any layperson can get their hands on, or is it some specialised kit that requires some training or at least instruction ?
Typically a locally-owned medical supply/drug store will carry them, although you can also order them
indivdually online. For most applications, the 90mm version (#4) is the size that you'll want. To confirm the airway is the proper length, it should reach from the patient's earlobe to the corner of their mouth.
As far as insertion, there are a bunch of
online videos showing the technique. The airway is inserted into the patient's mouth upside down until contact is made with the back of the throat, then the airway is rotated 180° to secure the tongue. No rotation is necessary to remove the device, as it follows the curvature of the tongue.
Despite what the linked video shows, OPA's are generally only used on unconscious patients, because of the high probability of stimulating a gag reflex.
Jim