This battle guide is very good. A lot of things are covered in this piece of work.
There are more ways to dodge a blue shell. In some cases, you can get hit by a thunder or a POW block before the blue shell strikes and it will negate the effect of the blue shell. It isn't common for this to happen, however.
Another way to dodge a blue shell is to get hit beforehand by bananas, item boxes, people with stars, or people with mushrooms (this method is best for Coin Runners). The blue shell costs you half your coins whereas the bananas, item boxes, people with mushrooms, people with stars only cost you 3 coins. In most cases, the person who is going to get hit will have lots of coins (probably above 10). Losing 3 coins won't be as bad as losing half the amount of coins the person has. Another good thing about this is that you won't lose your item (unless you got hit by a star). In fact, if there is a shell nearby on the floor, it is best to be hit by that rather than the blue shell. You might lose half your coins, but in the long run, you still have your items and you also recover more quickly, allowing you to grab most of your lost coins.
If you want to dodge a blue shell in Balloon Battles, you should probably go jump off a cliff (literally). Either way, you are still going to lose a balloon and your all your items. The good thing about falling off the course is that the other team won't get a point since the blue shell hits nobody. I wouldn't consider getting hit by the Chain Chomp just to dodge a blue shell though. That method leaves you vulnerable and slow, the perfect prey for red shells. Falling off the course allows you to spawn in a random location, giving your opponents less time to prepare an attack.
Whoops! Perhaps I have gone a little too far with the explaining. This is your battle guide, not mine.