I've just done some 'rivetting' to the top of a turret. I found PVA to be no good as it dries to nothing. Therefore, I next went with epoxy, mixed a little bit and applied with the pont of a cocktail stick. The first session and it went well, however, the rivets are diff sizes and some mishapes and diff spacing in there but it only took me 10 mins.
The second session I actually marked out where to put the rivets with pencil dots and I was more careful. But next day I found the epoxy had settled and the small raised dots had flattened into small flat circles that looked completely different to the first days... I had to cut them off.
The 3rd I took my time and just put a bit on and took pains to keep the line straight. These look great as they're all the same size, even spacing and they are all round headed and raised enough.
The moral of this is success, or not, I found is down to technique of applying the epoxy... you have to keep the footprint of a dab small and build it up while not applying to much mix.. or it'll settle like my 2nd session. So I'd practice on an off-cut of something and I'd get them right before before I worked on the actual item.
Re: scale. while Bryan is technically right, I think modellers have to create the impression that there are rivets there... it's about the look of the thing and the impression it creates over the technical sizes of things. That said, I do agree that huge rivets are more off-putting than none. IMHO.