Howdy MikeOD, got a quick suggestion and a little info for you. Definitely a good idea to augment the makeup of your soil. I like to mix my own but use both perlite and vermiculite. One causes soil to drain better and captures oxgen while the other stores water so that as your soil dries it releases its moisture. This combination keeps the soil dampness problem down to nil. My mix is 60% soil and 20% each of the 'lites' (or in other words, 3 containers of soil to every one of each of the other.) I like to water mine about every other day in most cases, but I use a rule of thumb which is about 1/2 inch of dry soil on top means time to water.

As to the Humidity question, humidity is relative. In other words the warmer the air the more moisture it can hold. Therefore the answer to high humidity is NOT to lower the temperature (this would cause the percentage of humidity to rise which could cause the plants to stop there transpiration process and possibly cause grey mold on buds.)

Buy a reputable grow book, information on these boards is often sketchy! Educate yourself and then others!