See the Pool School articles
Using Chlorine in a Spa and
Using Bromine in a Spa.
There are four main differences between spas and pools. First is that the bather-load is much, much higher in a residential spa compared to a residential pool. This means that the amount of oxidizer that needs to be added is mostly related to how many people are in the spa and for how long. Second is that spas are generally covered with no light and generally do not have algae as a concern. Third is that the water is usually at a hotter temperature which accelerates chlorine usage in between soaks but also allows for bacteria to grow very quickly (along with the high bather load that gives them plenty of nutrients) if the disinfectant level is not consistently maintained. Fourth is that due to the small water volume and higher bather-load, the water is periodically replaced in a spa (i.e. full drain/refill).
You do not normally use Trichlor pucks in a spa because with the hot temperatures they dissolve too quickly and with the small water volume it's too easy to overdose and have the pH crash if one is not careful. So for slow dosing, one normally uses bromine tabs instead. This works best if one isn't using the spa regularly (say, only on weekends) or if one has an ozonator that can make more bromine from a bromide bank. You can create more bromine from the bromide bank by using an oxidizer such as chlorine or non-chlorine shock (MPS). Usually one needs to periodically shock a bromine spa using chlorine to keep the water clear because bromine is a weaker oxidizer (especially if one does not have an ozonator).
If one uses the spa every day or two, then chlorine is added after every soak; if you do not soak regularly then you need to add chlorine in between soaks. The Dichlor-then-bleach method has one use Dichlor initially to build up the CYA level and then switch over to using bleach so that the CYA doesn't continue to build up. Alternatively, one could add pure CYA initially similar to what one does in a pool.
As for a chart with levels, for chlorine the CYA should be in the 30-40 ppm range and the FC should not get to zero in between soaks. Most people target 1-2 ppm FC for the start of their soak. The key is to add enough oxidizer after each soak such that there is still a chlorine residual at the start of the next soak.
Bromine is easier if you do not soak regularly because the slow dissolving tabs (or the ozonator with a bromide bank) maintain a bromine level in between soaks. It smells different than chlorine and some people don't like that. It's more expensive than chlorine (especially if one uses bleach).