Assuming you've used the mission restart method to get your 50 playthroughs done, this and
will most likely be your last achievements. For the turrets you'll just have to find a level with a few turrets close to spawn and keep restarting it, but for this one there's a wonderful method which will make it decently fast.
While you will run into loads of Goblin Rioters (the purple clothed goblins) through normal play, the fastest way I found to push my way up to 10,000 was to grind on the Dreadwalker boss. If you avoid shooting at his weak spot (the head) you can just keep killing the rioters he spawns every few seconds for as long as you like. The boss will probably eventually die from secondary weapon effects and whatnot, but in that case just quit out and restart the stage. The goblins and pink mines even drop health refills quite frequently, so you're not likely going to risk dying. Keep in mind touching the boss himself doesn't hurt you either, so feel free to keep running back and forth under him as much as you want. Doing this, it didn't take me very long at all to climb from the roughly 6,000-7,000 rioters I had after finishing everything else all the way up to 10,000.