First off, make sure you are properly weighted for the fresh water and the exposure protection you are wearing. Then realize that, unlike your prior experience with warm salt water and thin exposure protection (if any), a thick wetsuit is going to lose significant buoyancy as you descend. In the tropics, a couple of puffs of air is enough to compensate for the gas you are carrying; in cold water, you have to add a LOT more to compensate for the thick neoprene as well.
As you descend, it is a reasonable practice to add a little air to your BC each time you have to clear your ears. It will slow your descend, so that once you acquire a visual on the bottom, you are moving slowly enough that it is easy to stop. You can also get an idea of your sink rate by watching how fast the particles in the water are streaming up around you -- if they're going fast, it's a good idea to add some air to the BC and slow the whole process down.
Assuming a large enough air bladder (which most BCs do have) you can get neutral in any water. It's just a matter of putting enough air in the BC. And that's why you don't want to be overweighted, because that will just make it that much harder to get enough air in to compensate for weight you don't need.