Soak it and then gently wash the soil away. That always works better.

I am wondering why there is a need to remove all the previous soil. Are you attempting to dwarf it and avoid using a larger container? I have read that palm roots are sensitive so, there is a need to be careful. I understand the need to loosen up those girdled roots which you might be able to do by cutting with a clean knife or maybe sharp scissors. If you manage to loosen up the outermost roots, the existing roots will soon grow into the new soil.

Im getting rid of all the old peat based soil so I can pot it with 5-1-1 mix, im also going up in pot size so the opposite of dwarfing (hopfully)
The roots are very compacted together and knotted.
Ive manged to wash and pick abit more soil away and free up the roots abit, ive done this before on my Arecas and Palours successfully but ive had little experience with Kentias.
I was tempted to trim the roots around the edge of the ball but I thought id play it safe, if its ok to trim the roots in this way then next time I replace the potting soil I will go ahead and do that with confidence.
Heres a picture of the newly potted palm.

Thanks