I never used my ct 26 as a wet vac, but I did get the bucket insert and the sponge filters for my ct22 (They don't make that for the newer vacs, but with the older models the top was hinged to the tub, so it made emptying hard without the accessory.)
But I have 2 more work vacs and I prefer to use the hitachi I have; because you don't need a lot of suction power for wet vacuuming, and it's less powerfull than my ct's (the same vallues as the old mini/midi) so I can keep the CT's dry for woodwork where more power is handy. I also need to empty it less often, because it has a higher tub.
I got the compact cleaning kit with my CT22 as a free extra from my dealer, It has hold up pretty well, I replaced the floor nozzle after it broke(after about 8 years or so), and I worn the brushes of the small round nozzle and replaced that too.
BTW, I use the insert with the brushes for hard floors and the "groovy" one for carpets. (so the other way round as atomic mike does)
Back then festool didn't include a picture on the lid with the what goes where, and it's a bit of a puzzle, so I printed one I found online and taped it to the lid.