I will soon be at the stage in my builds where I will need to clamp the barrel somehow to put the flashiders on. I've looked at several vises made specifically for barrels but they're pricey. Will wood blocks and a regular bench vise be ok for this or should I drop the cash for an actual barrel vise? The goal here is to not damage the barrel or the finish. (Obviously) Any one with any experience care to chime in?

i can't recall using a barrel vise for a FS but if i did i used a basic set of blocks in a bench vise.  if you arre worried about finish you can clamp the barrel under the HG.  If you might be building a FAL then i would suggest buying a decent barrel vise.

why do you need to clamp the BBl to get teh f/h on, I never did

Blocks or a regular vise at the gas block -- protected from marking with thin plastic or copper sheet -something like that. If you find you still need a barrel vise let me know and I will loan you mine.

If you can clamp the barrel in a regular vise with some of those plastic jaw protectors --the kind with a groove for a pipe,etc (sold at Home depot, "wilton" brand) then If you need to stabilise or preven the barrel from turning more grab it at the flats in front of the receiver  with an 1-1/8in wrench --file the wrench flats to fit the slightly larger flats of the barrel. If the FH takes more muscle than that to put on ---somethings not right.

Quoted: why do you need to clamp the BBl to get teh f/h on, I never did

Indeed.