Pete, my husband "flunked" his swallowing test and wasn't aware that he was aspirating either. The speech/swallowing therapist was phenomenal and he saw her several times and had to learn how to position his head and neck a certain way to safely swallow.
Initially he could only tolerate thick fluids such as apricot juice but he eventually made progress over time and no longer aspirates and can eat just about anything now except for my well done chicken.
Good luck