Ditto on post #18 on the return trip from South Post Oak to IAH via the Hardy Toll Road. If it is rush hour, you should take it. You have to get on the 610 Loop going north.
Also, the OTC expo is at the Reliant Center. That is located on 610 Loop South. My earlier directions will take you right past it when going from Webster to South Post Oak. You would exit Kirby or Fannin if you intend to park there.
The difference is that if you take JFK, you then have to get on the beltway to either IH45 or US59. Hitting 59 from WCP and going south eliminates two interchanges from the logitech's route, easier for a visitor unfiamilar with the lay of the land to make fewer transitions, the old KISS principle
logitech, the freeways in Houston are marked very well, keep your eyes up and you'll have plenty of warning when you are approaching an interchange.