I have had sinus problems most of my life, except that my sinuses drained when I stood up, and clogged when I laid down. Turns out, I was allergic to my cat! D'oh!
Anyway.....if you don't want to steam up the whole bathroom, just boil a pan of water on the stove. TAKE THE PAN OFF THE BURNER (very important!) and set it on a counter, or on a hot pad on the table. Sit down, drape a towel over your head and place your face directly over the hot just-boiling water. Create a nice steam tent and BREATHE. Oh, it's best to take your glasses off before doing this. (heehee).
This is a good way to steam up your nasal passages.
I buy generic guaifenisen (Mucinex) from medvitamins.com, and I buy it by the CASE. I have it everywhere - in my purse, next to my bed, in my office desk drawer, next to my sofa seat.....it's my go-to medicine for nearly everything mucus-related. For the record, get the gelatin capsules rather than the pressed powder caplets. They stick in your throat. And drink, drink, drink. You need the fluids! I use a CPAP with a nasal mask, so a stuffed nose means No Sleep At All. I also have a neti pot, and that wonderful sinus rinse bottle. That is kind of awesome, isn't it?