I think the application should be done high and between their shoulder blades, actually right behind their heads....sorta on the back of the necks. My cats can't reach there themselves, but the reach each other's.

By staggering, the one with the application usually runs and hides....thus leaving the other cats to not see the problem...

Two weeks, well, within a couple of hours, the stuff is absorbed, so maybe staggering by day...AM PM...