I don't double dip for intimate waxing and wherever there is blood spotting other than that I dip as many times as necessary.
I am not sure why you would want to use both ends of a spatula, it doesn't look very professional ... the cost of a spatula is one penny, if you really don't want to double dip on legs then just use a new spatula each time you dip. Your client is worth that.
I would say you need to use 6 or 7 spatulas per leg if you are using them once. If you are using more than this you need to take another look at your technique.
Don't try to spread the wax with the flat of the spatula, you need to wipe the wax off onto the skin below the knee and 'scrape' it all the way down the leg to the ankle.
Alternatively you could switch to the cartridge system ... very easy to use.
xx