So sorry to hear of your broken finger!
Here is an excellent link that should get you started. There's even a song to go with it!
For a comparison activity, you could have the students cut out liquid items from magazine and/or newspaper ads (i.e. orange juice, milk...) and sort them according to greater than/less than/equal. After sorting, posters can be made. As well, you might want to bring in some containers for students to hold and feel the weights. Empty ones can also be used to make the Gallon Guy visual.
I teach 6th grade, but my students still need the visuals to go with the liquid measurements. I usually give them copies of my Gallon Guy (see attachment).