What symptoms are getting worse? In addition to the things everyone else has said, I'd personally worry if actual wheezing/gaping mouth/labored breathing were getting worse, but not over just an increase in mucous. Sometimes when an RI has more or less run its course you'll see an increase in mucous production/expulsion while you see a decrease in the more dangerous symptoms like labored breathing.

I'd stay away from doing anything inside the snake's mouth for now. Also, if you do decide to do something like that, use a Q-tip with relatively compact un-fluffy cotton at the tip (usually the cheaper kinds). That's what I use whenever I've had to treat mouth infections. It's a lot less likely to get stuck on saliva or hung on teeth than a cotton ball.