If air drying nappies on the clothes lines outside, avoid putting covers in direct sun as UV damage can occur. See Degradation of Fabrics for more information.
If using the dryer, depending on the cycle length, bamboo, cotton and hemp inserts will usually require two cycles to completely dry. Microfiber usually only requires one cycle. Covers can be dried in the dryer on a short cycle if needed, but air dry very quickly, even in cold climates. Wait till covers have cooled before putting nappies together. To save electricity use, nappies can be air dried, then finished off in the dryer.
Using the highest spin speed a machine can deliver in the pre wash cycle, removes water that contains a high level of poo and pee. The benefit for the main wash cycle is it results in the nappies drying quicker.
Spin cycles use centripetal force to push the washing against the perforated drum. Water is pushed out through the holes. Doubling the spin speed (eg from 600RPM to 1200RPM) creates four times the force against the drum, which removes more water. Centripetal force works from the middle of the drum outwards.
Some top loader machines can cause tangling, which can damage shells/covers.
If there is concern about tangling, or damage has occurred in the past, reduce spin speed in the main wash cycle (some machines do not allow this function) remove shells and re spin inserts to remove any remaining water.