We used to use wet pouches, though now we just use Royal Canin, for our cats and our dog.
However, drawing on past experience with pouches of cat food and a past career that included lecturing in fine art screen printing, I suggest laying the pouch on a flat surface and taking a straight flat implement such as the back of a cleaver or a chef’s spaula or perhaps a small piece of ply, then firmly draw the straight edge of your improvised squeegee over the pouch in the direction of the opening.
Alternatively you could open the pouches fully and let the cats lick them clean.
Look forward to reading other suggestions, there’s a great wealth of widely varied experience on SF.