hey i recently looked at the inside of my coolant recovery tank and it's got dirt and crap stuck to the sides of it on the inside

what kind of ideas can you guys come up with to clean this out??
a brush doesn't fit throw the hole at the top

 

I have tried a couple of things (soaking with detergents, brake cleaner, de-greasers) all with no luck myself...

I am thinking maybe of trying penzoil coolant flush next

 

Too bad we dont drive a VeeDub, they sell a new one for 12 bucks. Mazda ones are 90 some dollars