I do better practicing with a straight key. I simply hook it up to the leads on a vom meter with tone for continuity check set on the meter. Super easy to set up anywhere even if the sounds are digital and annoying.
I have a Lionel J38 and a Lionel J36 key. The J-36 bug's dit side is too fast for me to learn with even set up as slow as it will go.
I don't have a 2 paddle key and haven't played with one either.
You are welcome to borrow either or both, Dave.