1 liter will flush the entire system no problem. I use the ATE super blue with no problems. If the can has been sealed then its fine to use it, if it was opened before I would not use it. Moisture might have got into it. I would also suggest using
www.speedbleeder.com they are great. You should also get all of the fluid out of your clutch reservoir, wipe out with a paper towel and fill with some valvoline syntic, I did a complete clutch system flush and put the ATE super blue in the reservoir.