Used a medicine spoon, with and without a tube; and a travelmate. Preferred the travelmate, by far, because the receptacle is a bit longer, and slightly soft.
The STP I've been using lately, is a yogurt lid rolled into a funnel. The 'coffee can lid' thing I've seen tell of occasionally. Easy as heck, never leaked on me once, and it flattens into my pocket or wallet better than a medicine spoon ever could, lol.