Put a hand on your throat and start the buzz while your lips are still closed. You should feel a soft hum.
Release the lips gently, with no big puff of air.
At the end of a word, keep the buzz alive until the very last moment.
Now say: bad, cab, rob.
✅ Check
Say "pad" and "bad" back to back with a hand on your throat. Buzz from the very start means /b/; buzz only after the release means /p/. Then test the ending: "cab" vs "cap".
⚠️ Common trap
Letting the voice switch off. If /b/ loses its buzz at the start or end of a word, "bad" turns into "bat" and "cab" turns into "cap". Keep the buzz running right up to the release.