If you have the option, go snorkeling in a pool often
do partial mask floods, with water not obstructing your vision,
practice it with your eyes open, then just close your eyes (during the partial mask flood)
then do full floodings, then eventually everything should come together!
This progression may or may not come quickly, or easily.
Remember that you can cough into your regulator if need be, and that coughing is the body's innate way of clearing the airway.
Once you have the skills down, the real fun can begin! (diving, that is)