First, get a few new cellulose kitchen sponges. They don't have to be fancy, just be sure they are cellulose and not some synthetic that is going to dissolve in the dryer. Cut each sponge in half and place in a container with a top. I used a medium plastic storage container from the kitchen.
Then add one capful of your favorite scent of laundry softener. I smelled them all until I found one I liked. Downy has a great selection of intense scents that are designed to linger in the fabric.
Then fill the container with water, jiggling a little to mix. Put the container on the dryer and then every time you put a load in the dryer, just open the container, pull out a sponge, squeeze out enough liquid so it isn't drippy , then toss the wet sponge in with the clothes. It works like a charm.
Just think...if you were putting a capful in every load, the jug would last a couple of weeks probably if you bought the regular size bottle. ( the mondo price club size is shown above) Doing it with the sponges, The same bottle should last a year or longer. The intense scent, highly concentrated Downy was a bit more expensive than the house brands, but if we are talking one time a year, I can splurge at 5.99 for the Downy and 1.99 for the sponges.