Hi
The only methods that I am aware of in addition to the Von Schrader and HWE is hand cleaning with natural sponges.
There was another machine manufactured by George Holloways in London for many years called the 'Holloway Swift'.
Holloways are no longer in business but there are probably a lot of 'swifts' out there.
It is was a heavy machine which scrubbed the fabric using foam that was created by the fluid being injected into the brush and agitated on the fabric.
A wetter version than the Von Schrader which uses pre-generated foam.
Hand cleaning can be safer but doesn't give the 'deeper' clean of the other methods.
You could look at the low moisture tools that are available for HWE machines that may appeal to you.
I hope this information helps
Derek