Those "deep watering devices" are one of the worst things you can use. The majority of a tree's roots are in the top 12" of the soil. By using this attachment you bypass them completely.
Your trees would be happier if you used a small sprinkler and watered at the dripline and out beyond it. A tree's roots can easily extend out 2-3 times it's height. Don't water at the trunk.
Don't fertilize your trees until you can give them a good drink. The saying is "Don't feed them if they're thirsty"
You can put the Miracle Gro in any hose end sprayer, just set the dial to the correct mix. It won't really do the trees a lot of good but it won't hurt them either. You can also use any 10-10-10 lawn fertilizer.