I pretty much only use the PH/CL drops 3-way test for normal use. I keep my CYA at 65 and my FC around 8 with a SWG. My pool stays pretty stable. The only thing I need to adjust is PH that drifts up every 10 - 14 days. The CL only goes up to 5 I think on the color scale but I have a good idea what 8 ppm is as it's a bit darker yellow. When I want an accurate reading or if I'm slamming I'll break out the FAS/DPD. KimKats has a link to test kits where you can easily order refills. I always make sure I have enough refills in case of an emergency.
Understand, however, that the OTO test for FC isn't very good - JoyfulNoise, whom I trust with the chemistry side, says it's pretty much good for saying you have "some" FC in the pool, but not how much. I now use a high range comparator with a DPD test for daily FC testing (it goes up to 10 and is considered more trustworthy - look up Taylor 9056 test kit), but I still use the FAS-DPD test weekly to ensure I'm dialed in.