I tried everything with our piggies over the years .
We had a wooden pighouse for nice weather and in winter they came indoors to the small bedroom (no door and radiator off) with a big deepbased cage pr a C&C depending on what we needed .
Fleece needs an absorbant layer underneath, scentfree deteregent , no fabric conditioner and a PetBag to wash it in to protect your machine
We used - Megazorb, EcoBale ( horse beddings recommended for rodents )
a rodent safe wood based cat litter
fleece
piggie safe paper done in a confetti shredder
But really , what ours liked was cardboard (especially on C&C to protect their paws) , puppy pads , newspaper and a big box of hay (2 doors for safety)
If I gave them solid hay -maybe in summer , or if one had an eye injury , or maybe to curtail their mess ha ha - they'd just glare "Well this is a bit shit isn;t it" ?
Sawdust and shavings can affect them respiratory wise .
And don;t get me started in lemon or lavender shavings - they don't need fake smells . Just clean the bloody cage <looking at you Pets@Home>