I keep my sand and PVA glue in an old Chinese take-out container. I like that the glue fits and keeps me from having to store it separately. The glue, incidentally, comes two for a dollar at my local dollar store. Cheap glue works just as well as expensive glue for this.
When the lid is off, I use the container for dipping the models. That's why it's important to keep your sand in something wide enough to accommodate a flying base.
To get started, I apply some glue straight to the base, like so...
I use an old brush to smear the glue flat, making an effort to keep it off the cork and off the rim of the base. Then I scoop it into the sand. You have to scoop it almost as if it's a chip and you're trying to scoop up some salsa. It's the same motion. Once submerged, I swirl it around. It's critically important that all the assembly related glue is dry at this point or you'll glue sand onto the model proper.
Now, if you do get sand on the rim, just use your finger to wipe it off. This is PVA glue we're talking about. If you used something like super glue, the results would be terrible. PVA takes a while to dry, but is very forgiving.
That's pretty much it. I need to wait at least an hour (or more depending on local humidity) for this to dry completely. I'll probably go ahead and prime them at that point to prepare for painting.
I find the cork and sand thing works really well for bases. It gives you three different textures... the smooth rim, the rough sand and the stone like cork. Usually I add some static grass or grass tufts to add a fourth texture.
Here they are, ready for priming...
Once last thing. I always forget to close the cap and my glue harden in the cap. That's a pain. When I'm done with a container of glue, I wash out the cap quickly and toss it in with my other supplies. If I ever forget to close a new container, it's no issue as I usually have a few unclogged caps laying around.
