SadieKate I feel your pain! The first thing I would do is to talk to your doc about the non-sedating antihistamines if you can take those. There are also a couple of new meds out there too that are working really well for some folks who have trouble taking the antihistamines.
Saline sprays are very hepful in keeping the gunk in there loose and removable. Guiaffenesin (sp) is the stuff in robitussin that loosens phlegm and mucous and makes it watery - that helps me a LOT and it's over the counter under various brand names. Decongestants dry the stuff up and make it sticky so it stays there - you want to make the stuff as watery as possible so it runs out.
Sometimes I wish I had a miniature vacuum cleaner with a tiny hose!