By all means, pull the handle prior to folding the TM. My wife forgot to pull the handle once and after we thought we had fully dumped found out four days later (Mid Summer) that we had not actually dumped the holding tank. You can imagine the beautiful smell that had permeated the entire camper when we reopened it.
I use the powder packs for my re-circulating toilet and have found that by dumping one into a empty bowl after having emptied the system leaves a fresh smell in the camper. Thetford Envirochem Green has a fairly pleasant smell as compared to the harsh smell of the liquids.
Also, most dump stations have a water hose for rinsing out the sewer hose. Use this water hose to spray down any spills that are on the ground. The next RV'r will appreciate your courtesy.
ColoradoCop