"Apply a liquid fertilizer, diluted to about half the strength recommended
by the manufacturer, to the seedlings two or three times during their
growing season. "

But no one says how to do this. I water the plants with an overhead
mister/sprinkler combination that has worked really well. But when I tried
to use a small watering can to apply liquid fertilizer this evening, I
found it was really disturbing the soil in my nice little 4 inch pots with
gravel surfaces. Surely there is a better way, but I haven't seen any
reference to how to do this most effectively.