Yes, you do need to change your procedure. Never open the toilet while dumping as that will act as a vent for the vapors. Always keep water in the toilet bowl at all times. When flushing the toilet, do it quickly...very quickly, and then put about a quart of water back into the bowl.
FWIW...you don't need any chemical additive to contain odors. If you have an odor, you have a problem that needs to be addressed either with a repair or procedure. All chemicals do is mask the odor...doesn't fix it.
After dumping, put at least two or three gallons back into the tank. If you will be traveling after you dump, put in a cup of your favorite laundry detergent and it will slosh around in the tank and act as a cleaning agent. When you set up for the night, fill the tank with fresh water and then dump, flushing out all the soap and stuff. Add a couple of gallons back into the tank prior to using it again.
Others have reported great success in adding Calgon water softener to the tank along with the laundry detergent that supposedly will coat the inside of the tank and make it slippery. Sounds logical.
With rv black tanks....water (lots of water) is your friend.
Ron