Seriously, don't. It's complete and utter nonsense, just like those 'toothing planes' desinged to give the glue something to 'bite' into. I think it was Forest Labs, in the US, that did some testing circa WWII regarding what kind of joints held up best (they were comparing planed and sanded joints in wood being used for aircraft construction). Hands down, a freshly planed joint beats out a sanded/roughed up joint. And if it's tight, it's tight, and you won't find the glue line. I know I can't easily locate the centrelines on the acoustic tops I've jointed.
With the exception of epoxy, which likes something to 'bite' into, and needs to have glue left in the joint (ie, they're easier to starve), glues used in woodworking work best on FRESHLY planed surfaces, followed by freshly scraped, followed by sanded (I don't go past 220. Or below it, really). The reason I've seen bandied about for this is that a freshly planed surface is perfectly flat, there's no sawdust/contaminants in it, and you've got chemically 'free' ends on the wood fibres, that are looking to bond with something. Leave 'em out for a while, they're oxidise/reduce in the air, but given a chance, glue will do the trick. Undoubtedly, you can get good results with rough surfaces (glues have evolved, after all), but for the best surfaces, freshly plane prior to glueup.
As I understand PVA chemistry, it chemically bonds the two porous surfaces together. Sinks into the surface a little (works on porous materials only), and presto! The glue itself isn't very strong (cohesive strength is negligible; epoxy's the only one that's good at keeping itself together), ie any gaps/areas where the glue line is thicker than absolute minimum thickness mean weak spots. This is doubly true for Hot Hide glue.
Getting tightly fitting gluing surfaces is key. If you can do that with an edge tool (planes, chisels, scrapers), by all means to, sanding is good too, but don't go roughing up your surfaces unless you're using epoxy, which needs something to 'grip' onto, unlike PVA/AR or Hide glues.
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I'd like to see this smooth/rough gluing surface debate resolved to some extent. other than this post, are there any good arguments you guys can post?