You say you're using your bottling bucket as a secondary, but putting your priming sugar into it when you rack it? If you're going to use a secondary, the beer should be racked with no priming sugar and left alone for about 2 weeks to clear (usually into a class carboy), then you add your priming sugar to the bottling bucket and rack right before bottling. If you are adding sugar to the bottling bucket and then immediately bottling, that is not considered a secondary. If you add the priming sugar and then let it sit for a week or two before bottling, your priming sugar will be consumed by the yeast before it's bottled and you won't get proper carbonation.
I guess what's not clear to me is, are you bottling tomorrow or just moving it to secondary? Because if you're going to secondary, you shouldn't be adding any sugar at this time.
To answer your question, I boil the priming sugar with about 1.5 cups of water for a couple of minutes, then add to the bottom of my bottling bucket and rack on top of it. As long as your siphon hose is positioned at the side of the bottling bucket it should create a slow swirling action as it comes in which is usually enough to mix properly. I usually give a couple of slow stirs (no splashing) with a sanitized spoon to be sure it's mixed well, then commence bottling. There should be no need to wait for anything to settle.