brown sugar has gained some moisture, want to remove I assume this question generalizes to items such as flour. 

I kept brown sugar in the plastic bag it came in, in the refrigerator. Due to frequent use, it has built up clumps due to moisture. I've just recently gotten a glass container to store it in. Solutions I have considered to now remove the moisture are: 


Use a little uncooked rice to pull the moisture out

but then I think I should use a mesh bag to keep the rice in, where would I find something like this? 

coffee filter, too slow/cumbersome? 


Give it a little heat to dry it out, such as: 

place the glass on top of the oven with the oven on, as my oven top gets quite warm when the oven is on. 



Any ideas?
Refrigerating things usually dries stuff out in modern refrigerators, which tend to remove moisture, rather than retain them.  I agree with sourd'oh that drying is likely your issue.

It sounds like you are asking how to remove clumps.  I use a sifter, or try to move the grains through a strainer with a fork.  What are you using the brown sugar for?  Will it dissolve during mixing anyway, removing clumps (as in when beating cake batter)?