Piggybacked off nolem's work and made a thing that draws circles on walls.
The circle indicates the closest point on the wall to where the player origin will be when the rocket hits the wall if you were to shoot right now, based on your current velocity and gravity. I.e. if you shoot at the green circle and let go off all your movement keys the rocket should hit you. It's of course going to move if you strafe and whatnot so I'm not sure how useful this will be but maybe it will help out some new players.
The circle is actually 20 units below the player origin but that's because shooting at the same level on the Z-axis doesn't make sense most of the time and also so you can see the circle a bit easier without having too look up/directly sideways.
The circles looks pretty spazzy in this video because I was constantly turning while wallshotting which makes the circle also move since the rocket travel time changes.
Download:
https://github.com/laurirasanen/WallshotAssist/blob/master/plugins/wallshotassist.smxUse
sm_wsa for toggling it on and off.