Whether pillows, down duvets or down jackets, your down products should always be dried immediately after washing. Do not hang your down product on or over the heater; use a tumble dryer and set it to the highest level (up to 120 degrees). This is the only way to maintain quality in the long term.
If the filling still feels damp and lumpy after the first drying cycle, you should definitely put it through another. If the dryer switches off too early, the sensors can be tricked by adding in a damp towel.
To dry your down jacket completely and to get the best puffy, fluffy result, hang it freely in the air for 24 hours after the drying process and knead it well again and again.
Washing down pillows, down jackets or down products in general without a dryer is generally not recommended. The drying processes without a dryer can be very tedious or complicated, and you run the risk of the down permanently clumping together. If there is residual moisture in the down, mould can even develop, or unhealthy germs form. So it’s best to go to a launderette to dry your down products properly. If the label says that your down product is not suitable for tumble drying, you should ideally seek professional bed linen cleaning.