Without being toooooo graphic, have you tried an "aide" that can be purchased online or in an adult store?
Email me if you want more details. I can tell you what has helped me LOL.
My drive is still lowered bc of AD's but most of the time, with the help of an aid, the sneeze is completed
(My gf told me which one to buy & it works)!
Sending you the best-
Lisa