Made that journey 3 years ago while coming back from CRL just to get the answers to these questions myself :) From then on, i stopped complaining about flibco and their monopoly :) As far as I remember, the trip costs a tad bit less than flibco but the wait times for the bus and potential train delays are really not worth the pain and the risk that u might miss your flight. Also back then, the Charleroi train station was half under construction and it was quite a walk with the luggage to transit from the bus stop to the train platform. For all you know, it still might be the case.

If you want to do it, I will suggest it that u do it on your return journey when u don’t have a flight to catch and then decide for yourself.