Mary, every time I add soil to my raised bed (and I just added 10 gal. to plant some donated lilies), I add a mix of 2/5 Black Kow, 2/5 milled sphagnum moss, and 1/5 coarse perlite. I just mix my garden soil with this "potting" soil. My raised bed is loaded with perlite and each time I amend it, the perlite content is increased. It never breaks down, at least not noticeably, and certainly does open up the soil. All my potting mixes (not orchid mixes though) are typically made with that same formula.
