The first thing you gotta do is get to know your soil. Go outside a couple hours after a good rain and look around the areas you're wanting to plant stuff and see how wet it is at the surface and how wet it is a few inches down, 6 inches down, a foot down...
Then do that again the next day. See how long it takes things to dry out. That way you know how often you need to water if it doesn't rain.
Unless you have bad drainage you shouldn't have to worry about the roots getting too wet for too long. If you "overwater" a plant in the ground the water just runs off and goes somewhere else. Only when there isn't anywhere for the water to go because the soil is too dense or something is a plant likely to sit with wet feet too long.
If you're feeding liquid ferts you will probably want to do it when it hasn't just rained or isn't about to, because the more water there is in the ground the more the nutes can just run off to somewhere else and not feed your plants. You also want to consider how rich your soil is. Richer soil means you feed less because there's already lots of food for the plants in the soil. Poor soil needs more fert to make up for the poor amount in the soil to start with.
There's nothing wrong with time-release fertilizers if they're used right. The problem is that most people don't use them right or they get crappy cheap stuff that releases too fast or doesn't do it consistently over time. It's just as bad to have a big initial dose that tapers off quick as it is to have a light dose that explodes in a massive release after a few weeks. You need something that releases the nutes consistently over the entire life of the fert. I've used Heavy Harvest, made by Advanced Nutrients, and it was really easy to deal with.
Just don't combine regular ferts with time-release ones. That's another point where a lot of people make mistakes. And don't fall for the "if some is good, more is better" thinking. Twice as many nutrients don't make plants grow twice as fast. It just kills them.