A318 P&W
Biz pilot Brazil.
Hello, just leave the airplane in managed modes throughout the climb.
If you are flying for AV Brazil or Ocenan A. I can tell you that I have flown those 318s when they were at LAN, and as a matter of fact we still operate a handfull of them. That Airframe/Engine setup is not very optimal, engines are derated big time, and it may take you up to 38 minutes to reach FL350 when you are heavy.
If you go on V/S mode you loose airspeed and once you reach your cruising altitude those engines will continue to deliver CL THR untill you reach you managed Mach speed.
The airplane is underpowered and just as heavy as an A320, believe it or not.
Regards.