Having begun to learn the radio broadcast business in 1964, I feel we should all consider that we learn and improve each day. I've written and produced many commercials over those years and want to expand voice work outside the broadcast facility where I work full time.
Training? We don't need no stinkin' TRAINING! :) Seriously, I had on the job training starting at 13 years old by good professionals who taught me about clear enunciation projection and proper use of microphones, etc. A good example of what I do can be found at www.funradio us website. This is my "on line radio station" which I set up from scratch, edit all the content and program.
I'm using a Soundcraft mixing console for a mic preamplifier and have a UREI BL40 limiter and UREI LA-4 compressors for use when needed, although I use them very sparingly. Recall that earlier I stated that I want CLEAN audio, not smashed up. My main voice mic is an Audio Techica AT4033a condenser, I also use a Shure SM7 and a Behringer B-2 condenser. For field recording I use a Sony mini-disc recorder with a Shure SM7. Cool Edit Pro V2 is used for editing and I am is use an E-Mu USB voice "card" to improve SNR.
I've written a lot of commercial copy and news copy. I enjoy creating sound effects when I need them and can readily edit audio! I've been a broadcast engineer for 35 years and was an air talent and still provide voice over work at my full time job.