How long have you got? ;o)

I'd say a competent DMX programmer can do a simple show with Catalyst after one days training.

Understanding what is really happening with the content on the machine and the finer points of say the Colour FX channel is going to take longer and ideally involve some time spent experimenting with the system hands on.

Its a bit like Chess. Pretty quick to get started but depending on what level you want to reach a bit longer to master.

Some operators have said that in order to use Catalyst at the highest level you have to become a content creator yourself which requires you to learn other applications as well...