Alot of NDT companies have CWI inspectors. I don't know what your plan is as far as employment (what type of co.) but you could check about getting hired with an NDT co. Show you are a valuable asset and let them know up front you want to also learn about and become a UT inspector. If UT techs are in demand, then there should be no reason a company would not train the "right" person. I know quite a few UT/CWI inspectors. Most where UT then got their CWI and have also said they dont really use the CWI part of it that much, its just a good qualification. I am not a UT tech, but I do know a bit about the principals of it and how much it takes to be a truely good tech. You can't expect to do some training and go out and find a job as one. You couldn't do that with you CWI could you? You had to put in what, 5 years experience related to welding, and train, and study, and test. As I said, the right company should be willing to train the right person.
As for ET, I cant hardly remember much about it. I had some training on it in school, and with an NDT company I worked for. It seemed complicated to me. I do remember though, at the NDT company, there wasn't much ET to be done. Just every once in a while and the only one that did it was the level III. I think of it as on the same lines as UT, alot of training and experience to be good at it.
It never, never, ever hurts to learn about things. Just because you feel you may not become a UT or ET tech soon, read, read, read. It can only help you out no matter what. One thing you could do is call an NDT company (in Corpus there are alot of them) and see if they can refer you where to get proper training material.
BTW - I'm in Victoria