I paint the coins I will be basing my figures on first before I mount the figures. I use a cheap craft-store acrylic paint in a dull brown color (called mushroom) as my dirt tone. I suppose I should spray-prime the pennies too before I paint them, as the acrylic would have better adhesion, particularly around the rims. But I seldom bother.
To mount the figures I use a method I learned from ACWBill on this forum many years ago. No glue, no pumice, all done in one sitting.
The core ingredient is Acrylic Gel Medium. With this material I lay down the texturing of the ground, the paint for the color of the ground, and the glue to hold the figures and the flocking material all in one step.
For those who are not familiar with this product, the reference to "medium" is not placing it between small and large, but rather identifies this material as the carrier (the medium) for acrylic paints. If you are mixing your own paints you add coloring agents to this stuff. Basically is is the sludge at the bottom of the jar before you stir / shake your paint up. You can buy it at the craft store -- I bought this tub about 12 years ago and am now more than half way through it, so I hope to need a second one before I leave this world -- but that is not yet sure.
This stuff has the consistency of pudding. It is white in the jar, and dries dull and colorless, transparent if thin but opaque and taking on a dull gray tone if thick. If you add any acrylic paint and stir it a bit it will take on a diluted form of that color.
It provides the adhesion of your paint to the surface you are painting. It is also the reason that it's hard to unscrew the lid of your old paint jars. In other words it is a very capable glue. In fact it is sold as a household glue by several brands (for example Loctite brand sells it in a tube as glue.) I find it is at least as good as white glue ("Elmer's" in the US), but it is far easier to work with in terms of shape and color, and it does not shrink as much as it dries.
I take out a fair bit into a tub, put a few drops of my dirt tone paint into it and mix it around. This is then piled onto a penny to about 1/2mm thickness (as thick, or a bit thicker, than the cast-on base of the figures). I then push the figures into the glob on the penny. Then I carefully dab around the cast-on bases of the figures a bit with a brush to get the gel up to and even a bit over the edges of the bases. I then crumble a bit of model RR shrubbery over the stand, and sprinkle a bit of model RR talus (small stones) over the stand. If the troops are for Tunisia / Sicily I will then use a small dab of yellow model RR flocking, and sometimes even a bit of model RR static grass. I then basically bury the stand in green model RR flocking. And I'm ready for the next stand.
After about 15 or 20 minutes of setting time, I pick the stand up and tap it on it's edge to shake off the loose stuff. If some of the flocking stuck on the figures I might go over them with a fully dry paint brush to sweep it away. They are then left to dry fully (a couple hours maybe). And then they get 2 coats of Testor's Dullcoat to both ensure the colors are flat and to protect everything with an overcoat of hard enamel (it helps hold the flocking, shrubbery and talus in place).
Here is a view of the results. In this case a Romanian platoon HQ.
I use US 1-cent coins, which measure about 19mm in diameter, for my infantry. I also have tried to use Euro 1-cent coins for my half-stands, but the great advantage of using US pennies is that they are always available to me (I can always dig a few out from between the sofa cushions or under my car seat if I need more). I have tried to collect Euro cents during my travels, but alas travel has been a no-go for the past year and a half, and even when travel is available it is not reasonable to wait until my next trip to Munich to finish a project that is only 1 base away.
I have settled on a kind of standard for organizing my bases. The standard infantry squad is based 4 figures to a stand. Full sized special-purpose squads (ie: 8 - 12 men) are based 3 to a stand. These may be gun crews, command elements, engineers, etc. And smaller teams (support weapons crews, command elements, etc.) are based 2 to a stand. With these last two I will need to look at the figures to determine what kind of special purpose squad or team it is. But they are far less common than standard infantry squads.
So at game time it is easy to identify which are the infantry stands, where the special purpose guys are, and which stands die quicker (the rules I use make full sized squads of 8 - 12 men twice as hard to kill as half-squads of 3-6 men).
Here is a late-war Romanian infantry platoon. It is quick and easy to see the rifle squads, the command squad, the mortar squad, and the tank hunter team.