From what I understand, blocked ears are a result of having the eustachian tube blocked and thus the middle ear cannot equalize the pressure.
Pinching the nose and blowing is one way of dealing with it, but it can be painful and I also find it very uncomfortable. If you try to lean your head backwards and away from the side that is blocked, you can straighten up the tube and by a yawning motion with the jaw, you can create a free passage through the tube. If the blockage is only minor, sometimes it's enough to just tension the muscles in the back of the tongue a little bit and this will have the same effect.
This isn't a very scientific explanation, but I've had a lot of problems with my throat lately which in turn produces ear problems. Hope it was helpful!
/LnS