There's not much mystery to this - just apply the spackling to smooth out the contours. You can use your fingers (though that's probably not recommended - there are cautions on the tub...), or a putty knife, but for this demonstration I'm just using an ordinary plastic knife.
I apply the pink stuff to the base, giving it a gently sloping surface. The spackle is tacky enough to stick in place, but not so tacky that it can't easily be spread. I'm not worrying about getting it perfect yet...
The gimmick of this DryDex Spackling is that it changes color as it dries, so that you know when it's done. DryDex - dry index - get it?
Sometimes, I end up with a pretty smooth result on the first try, and sometimes I get lots of excess spackle on the figure - as you can see here:
Now, the next one turned out pretty good, though I got some spackle on the sides of the base. Fortunately, it comes off with water (or spit).
When it's dry (i.e., not pink anymore), you can use the plastic knife to smooth the surface a bit, knock off any parts you don't want, and so forth. The dried spackle is soft enough that you can actually use your fingernails, if you want...
Now the figures are ready for flocking (or whatever base treatment you had in mind).
One last comment on DryDex Spackle - it works fine in thin layers, but you get significant shrinkage if you use it to fill deeper gaps. Here, for instance, I've filled the slottabase bottoms and allowed the spackle to dry - note the shrinkage and cracks.
