When the bottle stops pouring and just drips, I wait a short time and then cap and toss the bottle.
I should do what my dad did is to have a spare "clean" bottle and let them drain into that. Then, even if it's a mix, it can be used to lube other things like door hinges, ect..
I leave my funnel in the engine for a few minutes, then I use and old bottle to drain anything left in the funnel. After many years, I have yet to need to change out that bottle.
Tom