Pentel Pocket Brush Pens - gimmie the details

[Katezila]

I'm a 2d animator and I had this idea to ink cels with brush pens, after using them to ink a different project. The problem is cels have to be inked with a flexible ink, like Higgins T-100 or Koh-I-Noor Rapidraw.
So I want to know if its possible to refill a Pentel cartridge with another ink, specifically one of these two, or is this a horrible idea that will mess up the pen?
Are there other refill brush pen options? Pentel seems to have two other options, "Standard brush" http://www.jetpens.com/index.php/cPath/221_517 and the "Aquash" http://www.jetpens.com/index.php/cPath/221_355 which I don't know if it could handle ink.
Does anyone have experience with any of these pens and experimenting with their ink supplies?
Thanks in advance!

[Kielbasa]

I've got a Pentel pocket brush pen and that standard brush pen you linked to. The second one is a water brush pen for watercolor. You fill the cartridge with water and squeeze water out, sort of eliminating the need for a water cup.

As for putting different inks in them, I've never done that. When you say Higgins T-100, do you mean india ink? I imagine india ink would dry up and ruin these brushes or gunk up the insides unless you cleaned it out when you're finished of course. If you really want to try it out, I'd get the water brush pen and fill it with something, and see if the ink flows out nicely. I think the inner workings of the water pens and the brush pens are different though, since ink is thicker than water.

[Zaknafain]

I've never tried the exact inks you mentioned, but I filled my brushpens with a wide variety of Inks and they hold up much better than traditional brushes.
I don't think it will be a problem at all.
Just one thing: NEVER mix Inks from different brands. It might work out, or it might end up in a nuclear explosion. I ruined several fountainpens, brushes and whatnot just because I was using two inks of different brands.

[Kielbasa]

So you refilled the cartridges with different ink?

[•Lindsay•]

I've filled a water brush with ink, it works fine. James Gurney (http://gurneyjourney.blogspot.com/2009/05/spiderwick-meets-dinotopia.html) did that also.