There is also what I think is called the 'Sheffield' cast where you stick your forefinger and middle finger in the loops of line coming from the first two and second two rod rings. Pull the line out letting line off the spool as far as you like and when you cast, keep your arm with the line at the same distance from the rod until you're ready to release it for the cast.
This will gain you several extra feet and maybe enough until you get used to the Wallis cast. I've also seen people do three fingers of line.
There's also another method I use that will get you 30 or 40 yards, but it's fraught with problems if you don't get it right and it's like casting with a reel that swivels around on the rod, like Ray Walton's reel. You have to hold the line coming from the spool in a loop formed with the forefinger and thumb of your spare hand and brake the reel with your rod hand's thumb. The loop you form with your fingers has to be perfectly closed and again, you keep that hand to the side of the reel and just inches from it all through the cast. It's like having a rod ring at the side, but as I say, it needs practice and can very easily go wrong.