There are drip irrigation kits for hanging baskets. They are a bother to set up but if you have many to maintain and want your baskets to have a humongous floral display, it would be the way to go. I tried the inverted water bottle method but that did not work well at all and I have returned to direct watering.

I agree with Loosestrife - they're all such a faff, these systems, and don't even seem to work very well, being unable to adapt between the vagaries of our weather here. One minute the baskets are being roasted all day, the next they're in full shade with rain, so with automated systems, they're either sodden or too dry.
I'm afraid I do it myself - with an old 1.5 litre Evian water bottle, with liquid feed mixed in when necessary, pouring all of it steadily and slowly into each basket either once or twice a day, depending on the weather.