I do this all the time for event photos. Once you get the workflow down it is very fast.
First, define your smugmug folder structure the way you plan to use it. Plan ahead -- people tend to make the structure too flat at first, meaning not enough levels. Works great the first year for basketball, but after a while you may find you want folders that break down by school or year or something else (to continue the sports example). You CAN create all this in lightroom, but you will also likely want to parallel this on Smugmug itself with home page links or drop down menus, etc. I am not suggesting you get the galleries created ahead of time, but the folders (think of them as scaffolding to hold the galleries).
Set up the Smugmug publishing plugin once, so it has your user ID and such, and review all the settings, in particular sizing, file types, metadata, and what things cause republish (I just check them all).
One thing that you may need to adjust over time is the "Quick settings". These are gallery defaults, in a sense. You can change these later as you get used to it, but you can also review and set up now. You can review every setting and see which ones you will routinely change from their defaults - things like maximum size or whether Print is on. These can be saved on smugmug as a "quick setting". You can have them different of course, e.g. a "Private client" quick setting or a "Public" or such.
Now once, on that same setting page, there's a "Sync" button in the middle. Check hierarchy and (usually) not check photos, and sync. This brings down down from Smugmug your folder (and gallery) structure and allows it to be seen on the publish plugin. It will keep it synced if you then use Smugmug only for doing things.
Checking "Photos" can be done if you have uploaded photos from your lightroom catalog and want to get them in the published folders -- it actually does a comparison of metadata and photos. It is for people who used SMugmug directly (or with a different plugin) and want to now convert and get them all in synch. It takes a long time, and you might get a LOT of "which photo is it" from the process if "Photos" is checked.
OK... after all that work, the rest is easy.
When you do a new shoot go to the folder in which you want your shots, and right click and "Create New Gallery" (ok, right click on windows, whatever Mac users do to get a context menu). Fill in the info, choose the "Quick Setting" as appropriate. Done. The gallery is now (as soon as you say OK) on Smugmug.
Now drag and drop your selected photos into that spot on the publish page. Right click (etc) and "Publish". Alternatively, open that gallery on LR and there's a publish button.
You may want to manually pick a "Feature image". By default it picks the first one I think. If you open the Edit Gallery dialog that's the photo by the description.
Once you get the defaults set this becomes very quick. After a shoot, the only thing I do on Smugmug itself is to manually position the gallery in a specific order in the folder -- Smugmug can do it by things like last date, etc., but I want a specific manual order and it cannot do that.
From that point on any time you change a photo that has been published, it marks it to republish. It does NOT automatically publish, you have to choose when and hit the button. You can publish a whole folder (or tree of folders) if you wish, and it brings them all current.
If there's an internet glitch and something does not publish, it puts up a dialog, and leaves it marked to publish. Just click publish again. It is pretty good at keeping track of changes you make, and what has gone up.
