I just applied mine as well! My backpack sprayer does right at 1k sqft for a gallon of water (slightly over by maybe 50sqft). My lawn is right at 5500sqft. Since my backpack sprayer is 4gallons, I put a little over 4g of water with 1.6oz of product and then again 2.5 gallons or so with .70 oz of prodiamine. I mixed the product in a solo cup really well, then dumped it into the container, washed the solo cup out and shook the backpack sprayer. I then put in about 2oz of blue marker. Seemed to work without any major issues. Hopefully, I did it correctly!
Nothing I would say was particularly difficult. The only problem that I had was that the blue marker was just a bitch. It just gets everywhere where you don't really want it to be and I was particularly careful with it too! I'm going to be applying one of my last rounds of N tomorrow and will water it in at night.