I keep coffee stirring rods on hand. These are plastic tubes, pretty cheap. One box does a zillion models. They also can be used to transfer small amounts of paint or thinner, pipette style.
I also do use pieces of sprue when there are lengths available. If I can find a piece with a J or L shape, I use this on older bottles that I haven't used in awhile, the hook at the end stirs better than the straight coffee rod if there is a lot of solids in the bottom.