but before new growth in the spring.

The main goal of pruning is to get rid of dead/diseased wood, and open up the plant so there's air circulation to the center. Definitely prune, but you may want to take it in steps and do a little every year for the next 2-3 years rather than hacking off too much at once.

I heard recently for blueberries to prune the oldest wood -- stems that look the most gnarled. I agree with not pruning too aggressively as you don't want to stress out the plant. If you prune to much, it might cause the bush to send out too many shoots and not many will survive with all that competition. An interesting thing I learned about pruning this past spring (this was for apple trees, but I think it would apply to blueberries as well) was to prune more on the south side of the tree as this will let more light in to the middle of the tree/bush and let more sunlight get to the branches on the east, west and north. You can also trim some branches that cross or are growing inward too -- so sunlight gets to the center of the bush better too. Always prune too above a bud that is growing out as opposed to inward (or it will just grow inward towards the bush) and don't cut too close to the rest of the stem or the trunk when removing branches (probably 1/8" above buds and 1/4" for larger branches at the base is good).