Are you talking about methods to get rid of loose surface wood fibres, or something else?

I had heard about this as well. Just before the first coat of primer, I wiped the body down with a slightly damp rag and let it dry. This raised a bunch of loose wood fibres which I sanded off with a fine paper (maybe 400?) running just off the direction of the grain. Did this help? I don't know. The first coat of primer went a bit fuzzy anyway as more loose fibres popped up. I probably could have skipped the whole wet wipe and sand steps and just sanded very lightly after the first coat of primer dried.

But that first coat got sanded back anyway with a sanding block as I tried to sand off the high spots. The next coat of actual primer still went a little fuzzy, so I very lightly sanded (pretty much just the weight of the paper) before the second coat. After that it stayed quite smooth.

But take all this with a large grain of salt, and see the disclaimer!

DC