Airliner Flying

I have been flying on MSFS for years. I have always used just the keyboard and have got quite good at it. However, I have never been able to maintain straight and level flight in jets, especially the airliners. I always use autopilot on instrument approaches until after crossing the outer marker, then begin a sloppy descent to the runway manually.
I was wondering if anyone has any comments about maintaining altitude without using the autopilot. Am I applying power incorrectly? Turning and maintaining altitude, airspeed and all seems impossible in FS. Is it easier using flight controls ie rudder pedals and joysticks?
I was wondering if anyone has any comments about maintaining altitude without using the autopilot. Am I applying power incorrectly? Turning and maintaining altitude, airspeed and all seems impossible in FS. Is it easier using flight controls ie rudder pedals and joysticks?