A mask, a bag, a fan, your hand, yes all those things would work, but you are probably not in the position to be using any of those. You’ve got a blemish that needs to go be covered.
There’s definitely an art to concealing blemishes. Over time I’ve found that the only tool that works is your finger. The heat and touch from your finger doesn’t work the same as any brush. You’ll save product by using your finger as well. The idea is to dab a small amount of concealer on the pimple. leave it for a minute, check in different lighting before blending it all away. When using makeup, blending is really important , but this is one time you don’t want to overdo it. If you can imagine using the concealer dabbing it onto the pimple in a few quick motions , then fanning out the edges to blend into the rest of your face. Surrounding the pimple you may need to add a lighter color or a little more concealer to make the transition even less noticeable.
In my experience green concealers aren’t really necessary. You don’t really need to “cancel out the red”. If it was a large area that was red (like a rash) okay , go ahead and use it, but in this case you don’t need to go out and buy green concealer. The color you use for under your eyes to conceal may not be the right match for masking a breakout. In fact a breakout is a perfect time to test out concealers for that reason. Next time you’ll be ready.
With blemishes I find the more you pile on the more it looks like a blemish. By adding and covering you’re only drawing more attention to it. The idea should just to make it look less angry, less obvious. No product will take the texture of it away or conceal it in all lights and situations. Realize there is still something on your face and that’s okay. If you can accomplish hiding it for the most part you’ve done a good job.