This is the bubble bar I am using today! It was a holiday one and it's called Gingerbread House.
I actually split this bubble bar into four pieces, which I could have made them smaller. It was two for one though so I'll treat myself to 1/4.
Next, I put the piece into a stocking like this. This was just an old stocking that my mom had and it only goes up to about half of the leg. If you don't have one like this you could always just cut a stocking so there is an opening that is easier to get to. After I do this, I just hold the stocking with the bubble bar underneath running water. I don't break it up or anything, I just let it run under the water until all of it is gone.
This is how it ends up! There is about 4x as many bubbles than the typical way that Lush shows you how to use the bubble bars. Not only that, but you can use less and still end up with more bubbles!
I hope this helps and let me know if this works for you! :)