Dude. This is the part of the graff experience where you get to pretend you're a ninja. Fuckin' do reconnaissance. Make a personal connection with that spot. Drive by it at various parts of various days of the weeks. Check to see how long they lay up lines there. Check to see what times of day or night they hump lines. Check to see how often other lines roll through there, and if they do, do they roll straight through or do they stop for a while? Then recon the surrounding area. Find your easiest ways in and out. Check into the surrounding businesses if there are any to see if they have cameras. Spend a day and walk up and down the line "benching" to see how far the next layup is or if there's a station down the line.
I've been driving by this one spot doing recon that I already paint for over two years now and I STILL don't have the schedule for it down pat.
Be a ninja, Homes.