Its fairly easy to use dry fertilizers. Doing a full line of liquid fertilizers is VERY expensive in the long run on a tank with a high nutrient consumption. Dry fertilizers are only really dry if you use them dry. You can certainly mix them up as solutions no different to liquid fertilizers. As far as how much to dose it depends a little. I would start will just a standard regime that you can find on any planted site. Something like the Estimative index or similar. Then kinda factor in any nutrient parameters that you know, like nitrate. You are free to modify the regime as you see fit as long as you dose traces and macros on different days generally. If your using a standard regime and you get algae or deficiencies don't be afraid to change the amount of certain fertilizers you add. No two water sources are the same, so think of the starting regime as more of mere guidelines. Just take changes slow. I would recommend aquariumfertilzers.com, thats were I get mine and is one of the cheaper places AFAIK.