Reinforcing is much easier to achieve than reducing

bbsadmin

How come Reinforcing is much easier to achieve than reducing?
One of my friend, I tried to take away his damp heat, it is very hard.
He has very yellow thick tognue coating, and red swallon tongue, but the pules is normal, not rapid, bitter feel in the mouth.
I worked on the liver and Ballbaldder, select Yangfu and XingJian, he didn't have any reaction, still thick and yellow coating.
Then I tried to work on spleen / stomach meridian, take Sanyinjiao, zusanli,shangqiu, lidui. He still have thick and yellow coating, but his appetites improve a lot.
Then I guess he is deficiency of yin causing hyperactive of yang, I worked on Sanyinjiao, taixi, taibai. He still have thick and yellow coating, but his speeping improved.

Would you please tell me what I have done wrong? How come I couldn't take away his yellow thick coating?
Thanks a lot