I've never had to do that, but I imagine it would be the same as transplanting into a bigger pot, but just the same pot. I'd dump it all into a wheelbarrow, mix in the perlite and or turface, crushed granite so you have areas where air can get to the roots. I'd then wash all the dirt off the roots and put the plant with the new dirt back into the container.
There is a dude on garden web that is the expert on well drained soils. Here is his recipe:
Al's Gritty Mix
For long term (especially woody) plantings and houseplants, I use a superb soil that is extremely durable and structurally sound. The basic mix is equal parts of pine bark, Turface, and crushed granite.
1 part uncomposted screened pine or fir bark (1/8-1/4")
1 part screened Turface or Diatonacious Earth
1 part crushed Gran-I-Grit (grower size) or #2 cherrystone
1 Tbsp gypsum per gallon of soil
CRF (if desired)
Source of micro-nutrients or use a fertilizer that contains all essentials I use 1/8 -1/4 tsp Epsom salts per gallon of fertilizer solution when I fertilize (check your fertilizer - if it is soluble, it is probable it does not contain Ca or Mg.
I don't use his recipe exactly, but I'm sure you need more than just perlite to get your soil draining.