Empty out your foundation into your new jar. You can keep it in the original jar, but it will be harder to mix(you'll see why later).
Im using a Covergirl Normal Skin liquid foundation I bought for 6 dollars at the dollar store, and an empty old jelly jar.

This is optional, but you can put a few drops of makeup remover in the original jar to thin out the foundation a bit and get the maximum product out.

Once you have your foundation in its new container, put a few drops of Proactive Daily Oil Control. You can use anything else of course, but i had that in handy. Keep in mind that adding too much will change the consistancy of your makeup. I stirred it with a clean paper clip, but use what ever you like.

I removed the label from the Covergirl jar and cut it to fit the new jar.

I decided to clean out the Covergirl jar and use it to store my paperclips.