You can add a constant downward dragging velocity to simulate gravity while on the wall, this can be best done with Mover constraints like Linear Velocity
If your wall run scripts already use a mover constraint, then simply add a negative Y velocity
In a movement demo I made, I use a VectorForce with Force value Vector3.new(0, 2400, 0), parented to the Character’s RootPart & Adornee’d to the RootAttachment
All I have to do is tick the .Enabled property to toggle the slow-falling effect