I wanted to make something up quick so I grabbed a tele homer and went to work.
Use an old cheap brush and dab it on the base. It's pretty simple just move it around till you like the look.
Next I painted it a darker grey.Then washed it with black to get the nooks and cranny's. Next I dry brush with a mid then light grey.
But if you want them to go further you can add some more and skip buying some resin bases.
An added bonus is its sticky nature. You can glue items on to make the base look that much cool. Just take some old extra bits or cut some new ones and add them to the base..
You can also add some plastic card + bits + texture paint to make it go even farther..