“Is it something I can use whilst in a attack or is it something I can only use when the feeling of an attack is coming?”
Methylprednisone might be a better choice when dealing with a fully-developped attack.
The problem with taking colchicine whilst in a attack is that you might have to take more pills and that you likely won’t get quick relief anyway. So you ought to take it early but taking it late sure beats having an attack which doesn’t end.
“You also mention your attacks can last longer but are those long attacks you get part of the same chain of days or are they spread across weeks?”
I haven’t had one of these for many years but they were like you said: “the pain gets better some days and worse other days”. To be clear: one joint affected by symptoms varying in severity but never completely going away.