I was in a similar situation this time last year. Out 11 years, former ATR FO with Eagle. I live in Atlanta, so XJT was the best choice for me. I applied on airline apps, received a call the next day, interviewed a couple weeks later and found myself sitting in ground school a couple weeks after that. This process will happen faster than you think!

I do not think you need to spend thousands on a transition course. Since I was not current, I had a simulator evaluation for the interview in a ERJ. I was very nervous leading up to that, but they put you at ease and are really looking for basic instrument skills. I spent about 5 hrs at a local flight school and paid a cfii to run me through the profile in a redbird sim (garmin glass and set up like a 182 or something). Best money ever spent. That will get your scan back and the glass is very similar to the RJ's.

I did not have the burden of the new ATP written regs, but xjt has a approved course and I'm sure others will follow.

My advice is to just get on Airline Apps, apply to any that have a base that works for you. Let them guide you on the ATP written.

Welcome back, pm me if I can help.