Softening a duvet cover

[bonkers20]

DS was given a duvet set for his Birthday. It's polycotton. I've washed it with softnener but it's still coming up rather stiff.
Do you know how I can soften it up? We had the same issue with a Stig set we got from Argos. Horrid. They took it back even after I'd washed it. But he really likes this one and I would be embarassed to tell the giver why we wanted to exchange it, having already told her he loves it...which he does.

Try adding soda crystals to the wash cycle. In the soap dispenser drawer. Oh and try tumble drying it before ironing it too. Polycotton usually softens with age.

Or buy a pure cotton percale topsheet.

would also suggest umble drying.

Thanks. I'll try all the above. Just went upstairs to find the duvet and pillow thrown out of DSs bedroom and him sleeping under his dressing gown and a blanket. I've put the old cover back on!