Or just take the 5.1 audio file and split it into mono WAV files (one for each channel) using software, of which there are many options. I use eac3to myself (yes, it works with DTS-HD MA).
The problem is, it’s still mixed - the center channel usually has some sound effects and music in it, the front left and front right often has some dialogue in it, and the front left, front right, surround left, and surround right are still a blend of music and sound effects.
Isolating just the sound effects or just the dialogue is next to impossible, but using the individual channels from the surround mix is helpful and standard practice for most fan editors.