Few questions regarding clutch master/slave
 

I'm replacing both and also got the ss flex line. The question is do I need a gasket for the master and do I need to use that washer for the slave to ss line? I noticed a gasket when I took out the master but I recall reading somewhere that I could just use rtv or something instead. If yes to the rtv, is it applied to the whole surface or just area around the rod that protrudes through the firewall?

I'd reuse the gasket if possible, if not, it's an easy one to make (which is what I did).

RTV has it's uses but in this case it seems like a lazy way out to me.

Yes, you can use RTV. You can use it in pretty much any system that produces positive pressure outwards. Just make sure that the mating surfaces are clean and dry. Apply it to all areas that the original gasket was touching. Be sure you give it enough time to fully cure...this may actually take longer than getting gasket material and cutting your own gasket...but it's doable.
As far as the washer, if you can use it, then yes you should reuse it. Automotive manufacturers want to keep production costs as low as possible, so they're not going to use any parts that they don't feel like the absolutely have to use.

How long do I have to wait for the RTV to cure? Not many places I can get gaskets at on a Sunday so I might not have much choice but to use it.

You wouldn't have to wait at all for the RTV...in this application you're only sealing the clutch MC to the firewall, which doesn't see much water under normal conditions.