I loosely followed the suggestions in the Marilyn Glenville Book "Natural Solutions to Infertility" -didn't give up many of the things she suggests giving up entirely (e.g. red meat, caffeine, alcohol, sugar) but did cut down on them a lot. Also followed her supplement suggestions. I found that this gave a dramatic improvement in my cervical mucus and I started getting "egg white" mucus where I did not before (sorry if this is tmi). So this might be worth a try
Maybe you were thinking of medicines for chesty coughs (Benylin chesty original)? They are supposed to make the bronchial mucous more runny and therefore improve a chesty cough by helping to get rid of the mucous. They also make cervical mucous more runny and therefore, easier for the sperms to swim.
Just wanted to add that I drinking grapefruit juice also helps with EWCM. I never had a problem with EWCM but since being on Clomid I didn't want to chance it so take the Evening Primrose (always used to for my PMT anyway), as well as drink lots of grapefruit juice. I'm also planning on trying out the cough medicine theory this cycle as it was mentioned to me months ago..
Regards the cough medicine mentioned...check out these links...