Gita, if you use Pro-Mix BX, it's not the right mix. It will get bone dry and hard as a rock. One of the best way to rehydrate it is to place the potted plant in water up to the rims until it stops bubbling and then let the excess water drain from the bottom. If the peaty mix is too fine, the roots will die of starvation due to soil compaction (rapid decomposition, especially of peat), That's why it's necessary to replace that type of soil at least yearly.
I don't know about the rice hulls, but I do know that you can substitute aquarium gravel or similar sized gravel (even a little horticultural charcoal) to add bulk to your mix, in order to give the roots some air space. I've also found chunky perlite at HD during the last couple of years. The ones in the small bags are mostly useless dust. Those are some options that may be available to you. Also soil conditioner (pine fines) and leaf mold are also good for adding to your potting mix. Someone, please correct me if I'm wrong.
Gita, on those beautiful plants found at the BBS this time of year, I find that first of all, they are often planted in too large pots with too much peaty mix. Sometimes the mix covers part of the lower stem (plant potted too deep) which subsequently rots, when the soil maintains too much moisture. When customers take them home, they are already dying, especially if they are watered/overwatered while in the foil and/or plastic plastic packaging. So I remove as much excess soil mix as I can without disturbing too many of the roots growing at the surface instead of down in the mix. (They don't travel down into the mix for moisture, because it's available right at the surface of the constantly damp peaty mix) Since I don't want to disturb the roots in winter, I usually remove at least half of the soil depending on the amount of roots the plant has and replace in the same pot or a smaller one. Then I'll repot it after it's dormant period/after bloom and the plant begins it's spring growth. I hope that some of this info helps.
