In a stall, remove the plug. If you're feeling bold, lube up a finger and play with your ass a bit. If you're feeling EXTRA bold, do it outside the stall! You can stroke as you do for a few minutes, but don't cum. When you're done, relube the plug and insert it again, then go back to your seat.
When you're ready to leave, take another 5 minute walk before returning home. Continue when you get back home.