Questions about using lava rock

[Orchid Whisperer]

I have a Dendrobium spectabile, an Encyclia cordigera, and an Epc. Charlie Brown that I want to re-pot into lava rock this summer. I would like a bit of feedback from users experienced with using lava rock as a medium.

It seems like red lava rock is the most commonly used type. However, the only kind that I was able to get locally is the black variety. The only difference between the red & black that I have read is that the black tends to get hotter in the sun; I think I can take care of this problem by using a layer of white quartz pebbles on the top of the medium (white reflecting light, etc.). Are there any other differences between the red & black that I should be aware of?

Preparation of the lava rock. My understanding is that the lava rock in the bag is unsorted & will need to sorted into very coarse, coarse, medium and fine grades. Also, it should be washed and rinsed to remove fine materials. Anything else? I was thinking that mixing styrofoam packing peanuts in with the lava rock in the bottom of the pot might be beneficial from a weight standpoint.

I have read that long-term care will need to include a monthly clean-water soak and rinse to remove salt build up.

Are there genera that do really well (or really poorly) in lava rock?

Any and all suggestions or advice would be appreciated!