mixing a little dish soap and water into your compound
It has been a while since is did it but it did have an impact on the air bubbles. 

How much soap ? Very little, much less than you think.

I have done the soap, maybe a half tablespoon for a gallon or two of mud, but i do not use any water.

I remember adding too much the first time and it was a little thin/loose, hard to work with. 

I used generic dish soap. 

You can always add more but you can not take it out. ( I have cut this board twice and it is still too short )