You can also try guaifenesin. You can buy some huge bad tasting pills or there is a liquid non-alcohol liquid version that is called a diabetic version since it is also sugar free. It is called Siltussin SA Expectorant. Ask your pharmacy for some. The pill is 12 hour but the liquid is 4 hour. It is really good and without the alcohol there is no burning.
Hope this helps relieve the goo dripping in the back of your throat. Make sure you work with a speech pathologist as well and find good excercises to maintain the constrictor muscles that direct or begin the swallowing as the radiation does a number on them. Mine have completely atrophied and the goo actually plugs up my throat from time to time. Don't be afraid to use a nebulizer with Acetylcystiene for the roughest thick days. I have a very radical remedy but will not pull that rabbit out of my hat until years down the road and you have a permanent problem.

Ed