When I was a teen I heard all sorts of ol' wive's tales about hickies. I tried them all, including putting a spoon from the freezer on it to putting toothpaste on it, nothing helped.
In hindsight, (looking back & all ), a hicky is a bruise just like any other. The fastest way I've personally found to get rid of it is heat & cold, just like you would do for a pulled muscle. It WILL take time, you cannot bypass it.
As for hiding one, I'll let someone else answer..... I got caught, big time, LOL.