I wish your doctor had been able to help you with this! Ive had the mucous suctioned out several times by the nurse. Its not pleasant but the relief I felt afterwards was priceless! Im surprised the doctor is not aware of how helpful it is to patients to use a portable suction machine. Which of your doctors said they never heard of this? Maybe try asking your radiation doc or their nurse.
Check out page 4 of the following document. Its titled Managing Copious Mouth/Throat Secretions
Christine SCC 6/15/07 L chk & by L molar both Stag I, age44 2x cispltn-35 IMRT end 9/27/07 -65 lbs in 2 mo, no caregvr Clear PET 1/08 4/4/08 recur L chk Stag I surg 4/16/08 clr marg 215 HBO dives 3/09 teeth out, trismus 7/2/09 recur, Stg IV 8/24/09 trach, ND, mandiblctmy 3wks medicly inducd coma 2 mo xtended hospital stay, ICU & burn unit PICC line IV antibx 8 mo 10/4/10, 2/14/11 reconst surg OC 3x in 3 years very happy to be alive