If I'm not mistaken, you are talking about wrapping the brisket with plastic wrap and injecting through the plastic wrap. It will keep all of "Butcher's Beef Injection" from getting all over and yes, if you put too much in one spot... it will be all over you,the counter,the floor.
Some folks will use a large plastic (food safe) bag and put the brisket down in it and then pick the sides up a ways. When done get the air out and seal for a few(4) hrs.
I do use David's product, but Kosmo's or Fab will make a decent product.
I've read on the internet about an injection that I've always thought sounded good. 2cups broth,1/4 cup Worcestershire sauce,1 tsp onion powder,1tsp garlic powder,1/2 tsp cayenne powder. Not sure who I owe thanks too for using this recipe?
I'm sure others will have some more ideas.