Water Blade:
The best-known US brand is The Original California Jelly Blade 2010 Version (equivalent UK Autoglym Hydra-Blade) is made of medical-grade silicone, which is very soft and flexible; it will not scratch the paint in and of itself. It can be used to remove water after washing the vehicle without causing scratches by applying very little surface pressure with the blade, wiping with long strokes in one direction only. The blade is preceded by water, much like detailer’s clay; this cushion of water should protect the surface against scratches, especially if you use a drying aid (Dodo Juice USA Time to Dry) to provide surface lubrication
If there is any grit left on the car after washing, the blade may pick it up and drag it across the paint, much the same as a towel would, this can be avoided by wiping the blade with a clean damp towel after every pass.
The water blade should be protected when not in use. If it is crushed in storage, the edge may take a set and leave a stripe of water on the car, the water blade comes with a protective plastic case, use it for blade storage.
Like any tool, the water blade does require a little bit of technique and practice. The first few times I used mine, it tended to chatter on the surface, resulting in incomplete drying. It turns out this is eliminated by using just the right angle, and pressure on a wet blade. Smoothness can also be affected by the surface condition of the paint (wax, sealant oxidation, etc.) and any coating that might be on the water blade itself.
I will add that I now only use this tool on glass surfaces, but that’s just over cautious OCD me
Caution: do not use a water blade to remove rainwater as there could be road grit on the paint surface or the rain may contain impurities that could scratch the paint.