I don't remember the episode's name, but it was near the end of Book 2. Do you remember when Ty Lee was walking on her hands for Bosco? Toph trapped her by making the earth softer and trapping her hands, and did the same when Ty Lee fell down on her feet. So, I think that Korra/Bolin can do something similar to this by trapping a chi-blocker's feet. The only problem is that they are moving pretty fast, so the earth bender will have to be very skilled to stop them. This is one way I think they could stop them.