Any watercolorists here?

I took up watercoloring about a month ago. I’m buying supplies slowly, as my budget allows, and I dare say that I’m already getting pretty good. You won’t see me hangin’ 'round the Louvre or anything, but my tries so far are not horribly offensive.

Last night I went to the store to get some new supplies, including a bottle of masking liquid. I’m not really sure what I was expecting, other than that the liquid should have flowed in a more-or-less paint-like way. I expected that I should be able to mask straight lines.

Instead what I got was little dried glops on the end of the brush. I had to dip the brush way down into the bottle to get anything resembling liquid, and even that glopped up pretty fast.

Is this normal? Should I be thinning it somehow? Or did I get some defective product?