I just watched the section where you took the screenshot from. It is an isopropyl alcohol pen. You can get them as CD writing eraser pens. You can just buy bottles of isopropyl alcohol if you want to use it to remove things.
CAUTION: It removes printing on the paper stickers!
Hope this helps!
-plarnold
I think I ordered one today on ebay although for my other hobby, it's called a gundam marker eraser.
@ Plarnold
Thank you for the help and the warning about the use on stickers. Does it say anywhere on the channel his name or screen name?
@ Ucwepn
Thanks, found about the only US seller that had them at a reasonable price. Also noticed that they sell a whole line of marker paints too for this brand. Is that what you are using for your other hobby and if so, how do you like them. I was confused as they call them both a marker stick and a paint stick which in my book is two different things.
@Super,
What do you mean by "his name" or "screen name"? His username is his Youtube account name 松岡純正 (99journey).
-plarnold
So its all those black lines that you added?
That is awesome. Really makes the model pop. Nice idea and work.