I'm no expert but here's what I have for advice.
Brisket in whole packer form makes great burger and is extremely cheap. Around here Costco flats are relatively expensive.
I'd rather grind up the point and use the flat for pastrami or for a small smoke dinner
I grind everything but the hard fat and only use one pass on the KitchenAide attachment using the larger of the two plates(considered a medium)
You'll see more of the fat(it will be whiter) then store boughten burger because it hasnt been mixed around alot.
I like to grind everything in long slices as it feeds better.
Pete-my first UDS,a brick pizza WFO, a leaky Chargriller offest, wifes Weber Genesis gasser,a Lightening Fast RED Thermapen, new baby Traeger