Hoya wightii ssp palniensis does best in a loose mix which is never allowed to dry out.  It likes to be watered a lot.  I think the only reason mine finally flowered was that it sat outside all summer long weathering temps any where from the upper 40s to the lower 90s.  It got watered when it rained which this summer was at least three times a week.  It received anywhere from 1-3 hours of sunshine when the sun actually came out.