it's not the meds you should worry about getting into the tank, it's the disease. Just "a good rinse" will not kill this and could carry over to the next fish you put in there. I have always used bleach, but I like the pottasium permanganate idea too. It's cheap, I got more than I could ever use for like $10. The only reason I think I would still go with bleach, is that it disappates extremely fast. Dechlor also won't get rid of potassium permanganate.
As for the water chemistry, just do water changes and fill with water from your tank. Take baby steps at first then go from there.
I have a net, heater, filter (sponge) and everything I only use in my hospital tank. Since I don't use it that often, I just throw the sponge away. A good way to filter, is keep a powerhead in your tank (small) with a sponge on it, have the same size power head in your hospital tank. (say a Rio 50, they're like $13 a piece). When you need to use it, transfer sponges and add a new one to your main tank. This will have the new sponge seeded by the time you need to use it again and an instantly cycled hospital tank.
Whole get up shouldn't cost you too much (maybe $25-30) and is always ready.