You need a Fast action to dodge one attack, so that you can normally try to avoid up to two attacks (using both standard Slow and Fast action) while doing nothing else that round.
Fast Footwork 1 allows you to dodge one attack under any circumstance, so that you can use the Slow and Fast action for other thing like approaching an enemy and make an attack. It's like a free action "on top"
Fast Footwork 3 is insofar different that you now have the
alternative to dedicate the Fast Action of a round to defensive measures. You must declare this, that's how we handle it in our group, because using Rank 3 plus Rank 1 appears unlogical and too powerful to be "opportunistic". However, if the Fast Action is dedicated to dodging, an unlimited number of attacks may be tried to be avoided once during that round. Note that Rank 3 "cancels" Rank 1. You either have "always one free dodge" per round, or you can attempt to dodge any incoming attack once.
Apart from that, the situational modifiers for anyone involved in an attack come into play, one by one per dodged attack, and these might change in the course of the round. This can be the type of attack (Slash/Stab) or through the defender being (already) prone. While prone the attack modifier is granted to any attack until the character gets up again, using a Fast (or Slow) Action. IMHO, dodging is still possible, but attacking from the ground is very limited.
Also note that Steady Feet 3 prevents a character from going prone through dodging. Expensive, but a great tactical add-on for professional dodgers.
