I'll ask if you shook the box really well before you tried pouring. All plastics will settle out some and need to be re-mixed by shaking or stirring. The portion that settles in Do-It plastic is thick enough to clog the nozzle. Its a good idea to shake your plastic regardless of what container it comes in at least every week or two.
I get the 5 gallon pails and before I do anything with them I pop the cover off and drill a 1/2" hole smack in the center of the lid. I use a paint blender that has an 18" long stem that fits a 1/2" drill. The paddles of the mixer go in the plastic and the lid fitted back on and fastened down with the stem sticking straight up out of the hole. It stays there until I haven't got enough plastic in the pail to mess with it, but I give that pail a good three minutes of mix time a week. When I am thru mixing I cover the stem with a clean towel, then a large plastic garbage bag to keep dust and other stuff from getting in.