Do use that walking foot - and adjust the top tension a little. Some velvet likes a looser tension. Also, sew in the direction of the pile! Like this:
(sewing machine foot) | V ______/ ---------------> direction of stitching
----------------------------------------------- \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ ///////////////////////////////////////////////
-----------------------------------------------
So, if the pile goes DOWN the skirt, you sew waist to hem. If the pile goes UP the skirt, you sew from hem up to waist! :)
You might also like to experiment with presser foot pressure: some silk pile and rayon velvets prefer lighter pressure. Another thing to try is the old zigzag-for-knits trick. Some rayon or poly backed velvet likes to stretch a wee bit, and sewing with a very narrow zigzag won't show on the outside but might just help it feed more evenly.