PVA/sawdust filler BEFORE sanding?

[CardboardPlastic]

Hi, my local timber merchant has offered me sawdust if I want to use it for floorboard gap filler with PVA. Can I fill the floorboard gaps with the PVA and sawdust mix and THEN sand the floorboards afterwards? Or is there a reason I shouldn't do this? I'd love to do the filling before the sanding for logistical reasons too boring to go into here!

I think the reason for doing it after sanding (and you use the stuff from the second pass with the sander as the first one will have muck in it) is to use wood that matches the boards.

Thanks Wooooo- so it sounds like it's fine to do it that way round, as long as the sawdust is a similar colour. I guess it just needs to be properly hardened before I start sanding.

I've tried it and despite using the sawdust from the second pass it was much darker than the boards and took an age to dry properly - not impressed!

User1471 did you use PVA glue, and did you do the filling before the sanding?