Sorry to throw my tuppence into the mix here but I have recently had great results with scale plastic rivets from Titchy Train Group.
This process is slow and time consuming as Trev quite rightly points out, but the results are very much worth the effort. It does require some time to mark out and measure up the lines and positions, but at least you can guarantee an even an consistent size and shape which is very difficult to achieve with other methods. These rivets come in a number of different sizes and they are quite reasonably priced too.
If you want to have a look over at my GP18 kitbash thread on this forum you can see the results I was able to achieve.