I'd just mix ordinary pva wood glue with sawdust.
Great, I’ve got plenty of that. Does it sand OK? Not something I’ve tried before.I use sawdust and pva, which very rarely matches the surrounding wood, so I tint the filler with acrylic, usually burnt umber. If you go darker than the wood it looks more natural than going too light. Water based finishes go just fine over these.
I watched this on Youtube last night and thought I would add it to this thread then found it's already here!This cheered me up - one of my favourite YouTubers...
Bit annoyed he did it in 3 days, I was going to say he obviously doesn’t have kids until he pulled out a packet of baby wipes.