I always did kind of good with vandas...until I heard Dr Martin Motes speak about caring for them. Then I started doing
really good with them
The roots should be misted heavily, until they turn green. Once the moisture "breaks through" the velamen (the white covering of the actual root) then you know the root itself is getting what it needs. Spray them well and if they don't turn translucent green right away, walk away, do something else for 20 minutes and then go back and do it again. Once you get this done the first time, you shouldn't have to do it twice again.
Lots of light and air movement too
Here in hot Florida, they get this treatment every day and in summer when it's v-e-r-y hot, they get misted more than once a day.