Of those i've only done CPL air law which was reasonably straight forward. The key is just to know where to find everything in your docs - and for a question which you have no idea about, know what you'd look under in the index.
The biggest hurdle for CPL air law is getting your head around those crazy crew duty time limitations. I flew four hours yesterday between the hours of 1500 and 1900, followed by a 15 minute powernap, after which I mowed the lawns at the flight school...........argghhh
