Alright guys, I want to introduce you to my favorite new tool! I picked up one of these babies over the weekend and I feel like stabbing myself with it for not buying it 10 years ago...
It goes by a few names and took me awhile to find exactly what I was looking for. It goes by deburring tool,  or triangular metal scraper. Its basically a tripled faced blade thats designed for removing burs from caste metal items as seen here.

I was building a few tanks this weekend and this puppy was amazing! It can clean flush against the hulls of tanks or flat areas and easily remove mold lines with the flick of a finger. I was actually excited to remove mold lines all weekend (yes you heard me right, excited to remove mold lines!). They are fairly cheap and I picked up mine through a machinist tools catalog that my father has discount access to. Cost me 10$ American.  I found a few off Google shopping for 11 - 15$. Here is a quick link to one: