Holy Sheet Batman .... what a title.
Our RN taught us to mark the long tube with a sharpie . If you hold it at the mark, when your fingers touch the lips, you can not go further. She had a way to measure from the front of your teeth , down to where your (flap that protects your lungs from aspirations ) . Sure , it will makes you gag , but its quick to grab the monkey snot, saliva, whatever caught in your throat.
It gets a little easier with practice.
Glen