Tried doing a search and didn’t really find an answer.
What techniques, or equipment, do you use to mix the Vallejo dropper bottles?
Mine have been sitting for a while and I am having a really hard time mixing the pigments. So, wondering how everyone else is doing it…
You can pull the little dropper part off and use a tooth pick or skinny stirring stick.
I have pulled off the top and used my handy dandy Tamiya paint stirring stick. But after you put the drip top back in place be careful when squeezing paint drops out. I had one bottle lose that part and shoot paint all over the immediate area. Not pleasant.
I personally hate Vallejo dropper bottles. I’ve had my share of “accidents” with them. In contrast, I LOVE Tamiya jars.
Ok, so it’s not just me 
Vallejo suggests:
I found this did not really do the trick so I tried adding an agitator to the bottles - in the form of some cheap glass beads (4mm) I got at Walmart. Now the paint can be shaken normally and you will get a good mixture.
I also read about another method and I use it as well. Chuck the bottle, by the cap, into your drill or cordless screwdriver and give it a couple of trigger pulls! Works great! 
My solution is simple
I put a Hematite bead in each of my remaining Vallejo bottles,and I shake them using that heavy bead as an agitator.
I also only shake them when the cap is still screwed on,that will hold the tip in place while shaking, as once you take it off of there, it is never again as tight a fit as when you first buy them.
BTW, adding to Dodger57’s post, this is what Vallejo recommends in their FAQ 2.7;
2.7. I have a problem with Model Color, it does not seem to go on smoothly.
The pigment may have settled too much. Add two drops of Crackle Medium (70.598) and mix the contents of the bottle by rolling it between your hands.
My Vallejo is relatively new, haven’t had to try this yet.
Chuck the bottle, by the cap, into your drill or cordless screwdriver and give it a couple of trigger pulls! Works great!
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This is a great suggestion. I’ll try that.
Honestly,chucking a bottle in a drill scares the heck out of me.i can just see me doing a Jackson pollack all over the room.that said I think I’ll give it a try too.
That’s an interesting tip, Chuck! I might try it too.
Kinda brings up an interesting physics question.given the inertia of the spinning bottle,do you put the drill on forward or reverse?
I’d already considered that. I figure forward, and then slow it down slowly.
Reverse and a fast trigger pull could be scary.
Hmm? I was thinking reverse
I’m thinking about securing a Vallejo bottle to a drill with rubber bands.
Maybe wrap a piece of tape around the cap and bottle?
Before I got these wonderful answers, the following was my method: I would take off the top and remove the dropper. Sometimes, a plug of pigment would be in the dropper. Other times, it would be clear. Then take Tamiya stirrer and mix contents. Then take bottle and place in Robart shaker and agitate for 5 minutes. I even started using the battery stirrer, but had to modify the bottom disc. Originally, the disc was to big to fit into the dropper bottles. This just seemed like I was making it harder than it should be.
The beads and the drill sound like a good idea…except with rubber bands [:)]
Quick tip…if you have a Robart Shaker, rubber bands work just as well as using Robart’s rubber straps. Three rubber bands and you are good to go.
Guess that shows I am an avid Robart user…