This is a real time- and money-saver.
I 've watched some tutorials online, and this is the method I use now:

What you need: 



A jar (plastic, glass, NOT metal) with a lid

A kitchen sponge (preferably two-sided)

Nail polish remover (or acetone)






Measure the sponge against the jar. Ideally, the jar should be half the height of the sponge.
You can use a larger jar that is the same size, or even taller than the sponge, but as you will only use it one nail at a time it would be a waste of space and acetone.







You cut the sponge in half and you place it as in the photo, with the hard side on the soft side.





    You squeeze the sponge and fit it in the jar as in the picture,
The reason you do that is that you can use the soft side to remove regular polish and the hard side to remove glitter polish.




You fill in the jar carefully and gradually with nail polish remover or acetone, so that the sponge soaks through and there is almost no liquid left.
You can use nail polish remover to be gentler with your skin, but, in my experience, nothing removes those glitter polishes as industrial acetone!
You close the jar with its lead firmly and keep it up straight.



Every now and then you put some extra acetone, in case the sponge feels too dry.
Ideally, you will change the sponge every month or two, depending on how often you use it. When your fingers come out coloured, you know it's time to change the sponge. You clean the jar with acetone and then water, you let it dry and you start over.

Puff! You saved money on cotton pads and/or store-bought polish remover jars!