Kyle, don't do it on the grill unless you have the grill set up to smoke with indirect heat. Use your smoker. There are a lot of threads on briskets so just do a quick search.
To answer your questions: trim the fat cap to 1/4" is the standard wisdom to start with. You can decide later if you like more or less fat. Fat cap on top to baste meat is also standard wisdom, but I put it on the bottom as a heat buffer (vertical smoker). That's a personal preference based upon my tastes and results I like.
The key to brisket is to leave it alone once you put it on the smoker. Just let it do its thing for at least 6 hours at 225-250F, no peeking. If you need it done more quickly you can go hotter and still get juicy, delicious brisket. Check the Internal temp, which at that time should be about 160-170F. You are shooting for 190-205F final IT, but more importantly you probe it with a tooth pick once in that range. It is done when the pick slides in easily like putting it in warm butter where ever you put the toothpick.
Looking forward to the pictures.
