Yes and Yes. The pre-filter when filling the spa will help and the metal gone type of chemicals with help remove suspended metals and minerals in the water that will then be caught by the filters in the tub. When I fill my spa I use both, wait a day or two then take the filters out and clean them, wait another day or two and clean them again.
Frog? Never really found good deals on their products but there are many internet retailers that sell them. I recently switched to the Frog @ease system and have had no issues but I have had to shock it once every week or two instead of once a month.
The pre filter I use is one of these but it sounds like you have a higher iron problem than I do.
http://www.spadepot.com/Pre-Fresh-Spa-Pool-Water-Fill-Filter-P2666I use about 1 bottle of a metal gone chemical per fill, There are many brands to chose from in this category
The other chemicals I use are pretty much those needed to adjust the chemistry (Ph up/down, total hardness, etc) most of which can be purchased at Walmart under the Clorox brand name, Once you get the water balanced after a fill you do not need to use much of these. I do add 1 ounce of SeaKlear Natural Clarifier when I shock to deal with bather related lotions/oil etc, a 32 ounce bottle lasts a long time in our setup and usage. The SeaKlear works like the metal gone products, it adsorbs the suspended oils/lotions and that then get caught by the filters. (Jacuzzi brand J335)