After trying to pencil for ink drawing using the 2mm Steadtler, I realized it was way too bulky and awkward, I need something tight and precise, and a hard lead that makes light marks and won't smear. So I got myself a couple of mechanical pencils. These seem perfect for the job (I say, having not tried it yet).
I'm not so sure about my less well-advised purchases of brush pens. The Pentel pocket brush pen is inexpensive and comes with cartridges that are called 'water resistant', but across the board everybody says they're actually effectively waterproof (necessary if you plan to do any wash work). Apparently the ink will withstand being held under a running faucet without blooming or running, but if you rub a thumb across it it'll smear. Might be good enough, but I don't like the spotty performance (might improve as I break it in better?). But the Kuretake sable brush pen is much better. Currently I have it loaded with Noodler's Bulletproof (which is very free-flowing unlike what I now refer to as PH Martin's Black Tar - which is a confirmed brush killer - sticks like napalm!) The thing about a brush pen like this though is - you need to use it regularly like once a week or so, or it'll dry out and become useless. And this is a rather expensive little instrument.
I think it might be a good investment if you draw in ink all the time, like if you're a professional cartoonist or something - but I kind of wish I hadn't bought these and just stuck with real brushes. They seem to be about a size 4 or 5, and I prefer drawing with a #1 or 2, or even a 0 or double 0. As for spotting blacks - I suspect a flat or bright or even a filbert is a better shape for that. Hmm.. would be kinda cool if somebody made flat or filbert brush pens, bur so far they seem to be made only for calligraphy, so all pointed rounds as far as I know.
A little factoid about Noodler's Bulletproof ink - it bonds to cellulose, which is a component of cotton papers (as well as cotton clothes). Once it's dry (couple of minutes) it's completely waterproof, though you might get a little blooming when you wash over it.
Just discovered what looks like an excellent page about brush pens. Wish I had seen this a couple weeks ago.
My latest experiments in makeshift inkwells. I tried the coke cap and the unidentified shallow clear cap beside it - great for brushes, but too shallow for pen nibs, And then I discovered the cap off the Spectrafix bottle, plus a similar one off a can of primer I bought for spraying the torso recently. These seem perfect. Clear, so you can see exactly where the ink level is, just the right width for pens or my (amazing!) Escoda kolinsky flat, and a nice smooth simple shape inside making it easy to clean (unlike the end of the Pentel correction pen next to it, which also seems like a good size/shape, if a bit tight).