I have the same thing for several years now, to me its the bodies way of expelling bad things naturally. You could try N-A-C, or N-Acetyl-L-Cysteine as that is said to clean out mucous in pulmonary diseases like cystic fibrosis.
It helped me detox but I had to stop due to 'healing crisis' as I'm very toxic and just try different things periodically. From my experience as long as you keep doing it you'll be alright, it was only when I swallowed the mucous that I developed bronchitis and submitted to Antibiotics .
Since then I always expel the mucous and never had a congestion problem again, it tends to build up after eating like you but could be anytime. Just get used to it by keeping something around or excusing yourself outside, I'm not sure its a bad thing. I have no comment on liver flushes, I'm still researching this.