As a Naval aviator, we routinely dumped fuel. In my type aircraft, we usually left a couple of thousand pounds in the wing where it was dumpable, and transferred the rest in. Landing gross weight limitations were absolute and had to be met. You were always saving fuel to better handle contingencies, and then dumping down to landing weight at the last minute, often on downwind and even into the groove. We often observed our wingmen's dump and our own. Depending on the rate of dump and airspeed, the fuel plume would break up into fine droplets and be invisible within a couple of plane lengths.
I've always been amazed at the amount of agonizing airline folks do over dumping fuel.
Swissair Flight 111 comes to mind. Instead of fiddling around with the dump, they would have been far better off to have turned on the dumps, point the nose toward Halifax, and come on down as quickly as possible (only under control this time).