Question
I have a Brassia signata(mexicana) plant is growing out of pot and sm. white roots are overside-having tbl keeping moist.  If I repot do I take of growths that have lost leaves and repot in approx. same size pot? What kind medium should I use?  

Answer
If you repot, the best time to repot is when you have new growths coming. You have some choices, depending upon the size of the plant and the total number of growths.  Count all current and previous growths, including those that are still healthy that have lost their leaves.  If you have 8 or more growths, you could divide the plant into two plants, potting each into sepsrate containers.  If however, the plant is smaller, or you prefer a speciman size plant, then repot as is.  Purchase a hobby bag of comercially prepared orchid mix at any retailer that handles orchid supplies (eg most Home Depots or Lowes carry this orchid potting mix).  Do not remove any leafless pseudobulbs as they provide energy for the new growths. I recommend a larger pot size if you are simply going to repot the plant without dividing it(usually a pot one inch larger in diameter should be fine).  Soak the plant in its current pot and, after removing it from its pot, wash the all of the old mix off from the root mass.  I also recommend soaking the new mix for a couple of hours before using it as the fir bark it contains repels water initially.