In general it's recommended to avoid adding any CYA until the SLAM is complete because as your CYA goes up so does the required FC.
I second the FAS-DPD recommendation, it's super nice to know exactly how much chlorine is in the pool.
How many gallons is your pool? I'd start by using some bleach to attempt to get your FC to slam levels, adding what is required per pool math and testing after 30 minutes. The experts here will commonly reccomend adding a maintenance amount of bleach until the test kit arrives, but I'll wait for one of them to show up to give you an exact amount of beach to add per day.
The TF-100 from tftestkits.net is a great value. It's usually advised to get the XL option if you're going to do a slam as it includes extra reagents you will use a lot of in the SLAM process. It also helps to support this non-profit forum.
If money is tight, you can order the fas-dpd kit by itself on Amazon for $20-25 bucks. It's a really good investment. There's no ambiguity like with the OTO or DPD tests. You'll know exactly how much is in there.
Edit: also giving your pool info (size, type, filtering equipment etc) will help when the experts show up to get you a quick recommendation. What is the current condition of your water? Cloudy? Green?