The test kit will be the best investment you make for your pool. It will allow you to test the water yourself and know what the pool needs. As you do this more and more, you'll be amazed at how easy the pool is to maintain. With a SWG, you'll really only need to add some muriatic acid every once in a while to lower the pH when it climbs. That's pretty much it. You won't need algaecides, clarifiers, or any other pool potions that the pool store is more than eager to sell you. All that money will stay in your pocket.
The key to the TFP method is monitoring and controlling the FC/CYA ratio. Get to know that really well. If you're having trouble now, there's a great chance that your CYA is very high which, in turn, makes the FC less effective at the normal levels you are used to. You either have to raise your FC to a higher level to compensate, or you have to do a partial drain and refill to dilute that CYA down to a workable level. Once this topic sinks in, you'll have smooth sailing. Just be aware that any hard chlorine (except cal hypo) has stabilizer (CYA) in it, so whenever you use it, you are also adding to the CYA level. That is the reason we recommend using only liquid chlorine or a SWG as your primary source of sanitation. They have no CYA or calcium in them so you won't be adding anything else to the pool that it doesn't need, only chlorine.