Mixing Vallejo Paint

[Dusky]

What are the best ways to mix Vallejo paint? Despite shaking a bottle for several minutes I found that the paint still wasn't mixed thoroughly. Vallejo's website says to roll the bottle on a surface. I've tried this, but it still doesn't seem mixed thoroughly.

 

[Elm City Hobbies]

Pop the top off and stir it up, the dropper top comes out of the bottle.