Sandpaper preference

[Kentf1003]

While doing some body work on my old Ford I noticed that my coarse (3M 40 and 60) sandpapers are doing a slow job when making the first cut on body filler. I remember similar paper doing a much faster job of sanding in years past. Is the paper of lower quality now?

What kind of paper do you Barners prefer when making your first pass on body filler?

Thanks.