I have a small plastic container (deli one like you get coleslaw in) that has about an inch of vodka in it.. when I want to clean an atty I let it soak in there over night or longer if I forget about it

It will get most flavors out! Rinse a few times when you pull it out and let it dry
If something tastes bad, my rule of thumb is you crossed the to much flavoring line! If it tastes light or you cant taste it at all, generally you need more. (always increase slowly, its a bit of work but so worth it in the end!)
Caramel Cap was designed to be extremely strong, start at around 1% and work your way up drop by drop to find your personal desired flavor.
Sweet Cream was not designed to be a major flavor in a mix, but as a subtle expression. Sweet Cream is one of the few flavors with a 6 month shelf life, it does not contain items that will go bad, but the flavor will decrease over time. It is not sweet, so if your looking to add creamy and sweet you may want to try something like bavarian cream instead