If the instructions say to treat daily or on a set schedule (every 1st, 3rd and 5th day, for instance) follow that schedule and treat the actual volume of water in the tank. If it says it's for treating new water, or if the directions are unclear, I'd treat the whole tank once and then just treat the water you prepare for WC.
I doubt the carbon will remove Stress Coat, as it is, I believe, primarily a water conditioner and carbon doesn't remove Prime.
If you're using Prime, I don't believe that you also need Stress Coat as they appear to perform all the same jobs. This is from Seachem's website:
"Prime® removes chlorine, chloramine and ammonia. Prime® converts ammonia into a safe, non-toxic form that is readily removed by the tank’s biofilter. Prime® may be used during tank cycling to alleviate ammonia/nitrite toxicity. Prime® detoxifies nitrite and nitrate, allowing the biofilter to more efficiently remove them. It will also detoxify any heavy metals found in the tap water at typical concentration levels. Prime® also promotes the production and regeneration of the natural slime coat. Prime® is non-acidic and will not impact pH. Prime® will not overactivate skimmers. Use at start-up and whenever adding or replacing water."
Hope this is helpful.