Some of the sprinkling devices showed that a lot of thought had gone into designing them. Begining with the 1960 Custom Imperial dryer, Frigidaire offered a clothes sprinkling system on some models that carried water from a compartment on the control panel in a tube that went through the rear drum shaft and terminated in a little plastic bump with a couple of holes for the water to sprinkle out. I have a Montgomery Wards Her Majesty dryer from the mid 60s that uses a very similar system except that the water reservoir is under a little square cover in the left rear part of the top of the dryer like where you fold clothes. GE had, for close to 10 years, an aluminum cylinder about 2 or 2.5 inches in diameter. The length was the depth of the drum. It had little openings on one side and a peg at each end, one spring-loaded. The cylinder was filled with water then set into position along a baffle in the drum. There were little holes at the front and back of the drum by each baffle and the spring-loaded end was fitted into a hole at the rear of the baffle, then the cylinder was pushed back on the spring to allow the front peg to lock into the hole at the front of the drum. In GE's first dryers to offer this, the no heat cycle was called Sprinkle, not Fluff and there was the symbol of a tear-shaped drop of water at the start of the cycle. Maytag Halo of Heat dryers had a white plastic reservoir that was filled then snapped in the place where the dynamic disc lint filter normally revolved. With the electronic control dryers, the Damp setting shut off at something just above Drip Dry so sprinklers soon became redundant. You would swear that Maytag thought people were still using Maytag rotary ironers and, according to the Miele auto dry control, rotary or machine ironers need the clothes to be damper than if they were being ironed with a hand iron.
Some more deluxe Kenmore dryers had a water chamber in the door that could be filled when the door was opened into the customary Kenmore position of lying flat in the opening, hinged at the botton. When the door was closed, the hole in the lower rubber stopper dribbled water out onto the clothes.
For cheaper dryers and idiotic people who had no idea of what they were letting themselves in for, Sears offered a sprinkler ball for the dryer. I brought mine to my desk so that I could describe it properly. It is a sperical object made out of pink plastic and about the size of a honey-dew melon. It has 8 feet (like a spider!)molded into the plastic at the base. They are in the shape of scalene triangles to hold it upright on a shelf or counter. On the bottom half of the sphere are three circles marked progressively from bottom to top: small load, medium load and large load. There there is a heavy equatorial rib that looks like the seam where the two halves are put together and projects about 1/8th inch beyond the side of the ball. This rib also looks like it gives strength and protection to the widest part of the sphere. Above the equatorial rib, are two setbacks at roughly one third and two thirds of the way to the top capped with a flat area each containing a ring of holes. At the very top is a ribbed cap that unscrews to permit filling of the ball. On two sides of the ball in the area between the two rings of holes is the message: USE AIR SETTING ONLY.
Anyone who has dried laundry in a Kenmore or Whirlpool dryer knows that the steel drum has a way of amplifying sound to where a couple of belt buckles or a few pieces of change can sound like the room is full of Flamenco dancers in full fury putting their castanets through an endurance test along with several city blocks' worth of inspired Slavation(sic) Army tambourine players. Now you fill this sprinkler ball with about 2 cups of water and throw it in with a load of fabrics that need to be sprinkled. Within seconds of starting the dryer (on the air setting), you realize that you will have to leave the room, close the door behind you and either go to the other end of the house or outside. If the dryer is in the basement, there is no escaping it in the whole house because the loud crashing noises will travel through furnace ducts to every room. It will sound like you are using the dryer to tumble a large rock and the shudders and loud sounds of impact will cause you to think that it would have made much more sense to damp dry the damn clothes in the first place instead of trying to rewet them.
Those are the main methods of sprinkling clothes in the dryer that I can remember. If I have omitted any, it was probably due to ignorance of their existance or sufficient hatred of a brand that caused me to blot out any memory of it.
One other thing that works quite well is to take a couple of heavy towels, soak them then partially wring them and toss them in with items to be dampened. You can do this with a Filtrator dryer, a condenser combo or water dryer by Maytag or Hotpoint on heat and steam wrinkles out of wool suits. It will restore wrinkled and crushed velvet & corduroy and do everything but make a silk purse out of a sow's ear.
Clothes that were damp or dampened were wrapped up in plastic and refrigerated the night before they were ironed. In the South I think it was to eliminate the possibility of the items souring in the warm temperatures, but letting them sit did make them more uniformly damp.