If you're gonna do any top watering along with the top dressing, I would suggest do your top water, let it settle for 30 minutes, then fill through tube. Otherwise you could end up with mud--especially in the jr's. Helps to tube water to runoff for a few seconds to flush out the old water. If the runoff smells rancid, run a good amount of plain water to flush the old stuff out.
Lately I've been making a "tea" from my top dressing and running the water down the tube. I think it works better for autos.