I didn't learn them all at once! Most fractal programs are similar under the packaging, and its easy to switch between them.
Mostly I search out tutorials and follow until I get the hang of things, also the library is great for 'How to' books.
I hate reading the manuals! So boring.
I was glad I learned Illustrator, it gave me a great grounding in using the pen tool that has been invaluable in Photoshop.
Zbrush is just plain fun.
Do you use Chaoscope? It gives fractals that are very different to Apophysis.