I had trouble getting down blocking, I am still having trouble getting down on both knees, but I have gotten my natural reaction to almost always dropping down on at least one knee, attempted to get my body in front of the ball, and rolled my glove over. It is a huge improvement from the beginning of the year when I always tried to pick it. As long as your have a good chest protector, it wont hurt. A lot of people think, a foul ball off the chest hurts somewhat, so a 90 mph fastball will to. When you actually do it, and after the ball has hit the dirt, it has lost most of its speed and momentum. Especially if it is a breaking ball, it probably doesn't have much speed on it anyways. In the end, try to make a game out of it, or if that isn't your thing, have fun doing it or something.
Just have someone go up to the field with you, even if its a sibling, and have them throw them as hard as you can, trying to hit the dirt. Draw a box or something where they should hit it, and have them aim there. If they don't want to, tell them it will be like being able to hit you without getting in trouble for it.