Walker is just now shipping newly devised brushes for the three steps of his Prelude. I just got some but haven't tried them yet. They look good but I can't vouch for any special effectiveness. I have found that stubborn spots will elude all but the most vigorous scrubbings. For stubborn spots I use a stylus brush with liquid of some sort, following up with the usual wet vacuuming. I've heard that vinyl is not impervious to such scrubbings but I haven't noticed anything audible.
When cleaning vinyl - what to use for
I read with interest a recent string about a fibrous residue after cleaninig which string also included a lot of detail about various vinyl cleaning preferences. Common to many procedures is a first scrubbing step. Am curious about what applicators/brushes are recommended for the initial wet cleaning step. Some have cautioned against a Hunt brush but also seem to indicate carbon fiber won't work effectively - just curious what IS used.