Thicken paint?

The rustoleum in a quart can doesn't seem to be very thick, nor flow/cover well. Especially upside down on undercarriage stuff.

Is there anything that can be done to make it better? Im looking at brush application, white/light grey color

Is it thoroughly mixed?  That is, none of that thick stuff settled out on the bottom?  Stirred, not shaken?

I've not found Rustoleum to be all that thin, but I haven't applied any in a few years. 

Apply it with this roller and feather it out with a foam brush. It will still take 2 coats so wrap the used roller in Cling (Saran) Wrap until the second coat.

See if you can get the can mixed at a local paint seller. I brushed the roof of my racecar with no issues. One coat covered great.

Sounds like i may have gotten bad product. Ive stirred, shaken, changed brushes, etc with no joy. 

Thanks y'all.