Step one for learning kansai-ben: throw out all the books you have on the subject and never buy any more. They tend to conglomerate all the different kansai area dialects into one dialect, and include many obsolete or gender specific words with no notations. A good example is "moukarimakka" which NO ONE actually says in real life but is the first thing listed in every kansai-ben book I've seen as a "common greeting". Even kansai-ben on TV is often exaggerated for effect. If you just want to understand kansai-ben that's fine, but I wouldn't try speaking what you learn from books or tv.

Unfortunately the only way to learn to speak it is to spend a lot of some with kansai people who actually use the dialect (many prefer Tokyo dialect so that they don't look like inakamono).

Really though I don't recommend learning to speak the nonstandard dialect in the first place. You will look silly (picture a Japanese student learning to speak some backwaters Texas slang complete with drawl), it can't be used in polite/formal situations without appearing rude, and it takes away from time that would be better spent learning/using standard dialect.

As to textbooks, you have to start somewhere.  They're all pretty limited, even for standard Japanese.  Like I said, it's nice to have the lyrics to Rokko Oroshi.

As to speaking ksb looking "silly," I've had a totally different experience than Jarvik7, though I admit my speaking of it is very limited.  I lived in a small Kansai town for a while and got lots of traction with the locals, who spoke mainly in their local dialect day-to-day and also joked about how their town had a different -ben than the town two stops down the line.  It's fun local flavor, esp. since Japanese always obsess over the furusato.  Also, I think any hypothetical language learner would know not to use it in polite/formal situations so long as they've had a month of formal Japanese instruction and a few weeks paying attention to people around them.

Finally, Kansai-ben is hardly a "backwater Texas slang complete with drawl."  It's a major dialect with vocabulary and conjugations that regional variations of American English can't equal.  Besides, if anyone comes to the US and winds up speaking like a local, I say more power to them.  Accents are great, and so are dialects.