On the question of how early you can start making it rain- If you are like me and start from clones it's possible to start making it rain about 10-14 days after you have first transplanted your clone into it's permanent pot, but you wan't to go easy on it the first few times. The plants ability to wick up the moisture is directly tied to how developed it's root system is, as well as it's overall size, so a little 10" plant thats only had a week to put down roots isn't going to be able to handle as much as a larger, more developed plant will. One note though- by using this technique you are essentially tricking your plants into believing they are in a much wetter climate, and they will respond by sucking up water much faster then you thought possible, especially the moderate waterings that come in between "rains". It doesn't happen overnight, but after a few weeks you will notice some major differences in your plants water demands, as well as in their growth.
My two largest plants are requiring between 1 and 1 1/2 gallons of water every other day currently, and actually prefer to be given about 3/4 of a gallon daily with a once a week 3-4 gallon rain (I use 5 gallon pots). I have already discovered that I can't go past that two day mark without the plants wilting severely, and I'd estimate that there's a 50/50 chance that I will have to move up to daily waterings to keep them happy for the next 4 weeks before they are harvested. The set of plants two weeks behind them are in smaller pots (partner bought 3.5 gallons instead of 5 gallon), and I'm already needing to water those pretty much every day. As for my vegging plants, most of those now require water every 2-3 days, though the youngest of them may take as much as 5 days to wick up all the water from a rain.
Keep in mind, that everyone's grow is going to be slightly different. If Riddle and I were growing the same strains we would still have some difference in how things work even though we live within 15 miles of each other, because our indoor environments are different. I use more intense lights and run higher temperatures in my rooms, so my plants will probably demand more water then his would. Point I'm trying to make is that you can't follow anyone else's schedule exactly because everyones' grow is different, so you are going to have to spend some time learning to read your plants. When it comes to water, the signs are pretty obvious though- A plant does not have a skeleton, so all of it's rigidity is the result of water pressure. If the plant/leaves are all drooping it's a pretty good indication that there isn't enough water being sucked up to maintain enough pressure to keep the plant/leaves standing upright, and giving it a good drink will cause the water pressure to increase so quickly that within an hour or two you'll never know there was a problem. True, overwatering can produce the same drooping effect, but it is usually accompanied by a lot of yellowing/miscoloring of the leaves very early on. That doesn't usually occur with underwatering until the plant has depleted every drop of water available and is starting to die. And frankly, I've found that it's actually quite difficult to overwater a mature plant. Too much water will kill seedlings and young clones easily, but once a plant has been vegging for 3-4 weeks it seems to have developed the ability to suck up pretty much all the water the dirt in the pot it's planted in can actually hold.
