I’m new so maybe my perspective will be helpful for another new knife maker (I’m on my fifth knife only).
You can find a ton of good info from others here and from YouTube on making handles, but here is one thing that I’ve learned from blemishing a couple knives myself, which you’ll later see was good advice:
Make sure you have things fitted closely enough, before final construction, to where you don’t have to grind down the pins too much. This is particularly true on bolsters, because they show any small imperfection in this regard. You will end up grinding past your peen, and even if the fit is very tight, this will give you a noticeable gap and the pins will be visible. If you can shape and grind stuff before it’s all put together, that’s always a plus. In some ways you can’t do this, but anywhere you can, do it.
I did this the first time on a knife, and you can see the pins. I thought, “damn I shouldn’t have opened up those holes with the hand drill to let the pins slide in easier, next time I’ll make it tighter”. Ok well next time I end up making the fit very tight on my brass bolster. I had to hammer it all together (it was a pain because I couldn’t just slide them in nicely, so also a negative in terms of time/effort). I ended up having to grind the bolster down to size, naturally, and I ground past my peened area and it shows a gap (a smaller gap mind you, but a gap).
So for doing pins in a bolster, make sure your holes aren’t too sloppy (yet you can have enough room to slide the pins in without being the Hulk), but most importantly make sure the thickness of the bolster is near its final state, because when you grind them it will show otherwise.