Hi Phloptik,
I’m certain you have a clear idea of your request, but I have to admit, the short question here is kind of cryptic. (Step, Spline, Control Weights, Paint Weights.)
Would you mind to share an example scene, a sketch or something like that? However, perhaps I got your point, and then the answer is: there is no weight brush options to my knowledge. Would be nice, I think I have had mentioned that ... but please feel free to suggest that to MAXON :o)
I have attached a little scene-file. I used “BodyPaint 3D” here to store the values of the “paint” and use the Shader Effector to translate those values into weight. The Plain Effector introduces no weight in my example, as I have set its value for weight to zero. As the weight change introduces movement here, the paint process might be weird or at least abstract the greater the introduced changes are. Just an idea…
All the best
Sassi
https://www.amazon.com/clouddrive/share?s=Srb1aiZNRSwnwwVUhB8DcA