First, drop a paint can down as low as you can, then use it to paint down in between two of the pet carriers of the same color.
Now remove these blocks, and work on clearing the blocks above them.
Take away any blocks between the next pet carriers, so they can slide together. And save these pets...
Then the remaining carriers can slide together!
Release pets from joined carriers, and continue to clear above them.
The remaining paint can could be used for any blocks without matches, or simply to gain more points.
Clear the blocks and rescue the pets.
Not all boards will have the correct blocks to complete the level this way, so if you do not have boosters to help, keep trying until you get a good board.