Cleaning the scales and glide area to equally maintain cleanliness and sealant of bases can be achieved fairly easily for better glide and longevity. Clean the entire base with cleaner, let dry, wipe, wax, let dry 5 min., and polish. The glide area can be hot waxed for best performance but is counter productive in the kick area (scales or patterned base).
Using a spray wax on the grip/kick zone (the cut-in, patterned base or raised scale area) will improve glide, especially in warmer conditions when the snow might tend to stick and slow you down. This is probably more of an issue on single cambered BC skis, versus double camber skis, where the kick area maintains more of a continual contact with the snow.