bottom feeding can work, but yo uhave the risk of mineral buildup at the top over time. top feed is better because the old excess can drain out the bottom. with soil you don't want much runoff unless you are fixing a problem in the root zone, but a minimal runoff assures you got the whole thing wet.
how often you fertilize depends on how concentrated a dose you give. every third? every other? just depends on how much you give when you do fertilize. convenience and personal opinion are invovled. it's generally better to feed more frequently at slightly lower cocentrations than piling it on. but, it's easier to pile it on.
wait for top 1" to dry and repeat. always get teh entire pot wet. if changing the formula or reacting to a toxicity issue, some extra runoff is always an option.
if you want to water more frequently, not jsut fertlization, you need a properly sized pot to plant and good drainage qualities. root rot is a concern if it is too wet all the time. early on a more conservative wet-dry cycle, like waiting for top 1" to dry, will promote a better root zone. later on if you increase frequency, you'll have a more robust root mass to handle it and the drainage to avoid issues. (50/50 with soil // 70/30 with cooc.. anything similar to perlite works fine.)