Re: bad experiences so far :(
As a starting point for the idle screw I would back the screw all the way out enough so it does not push up on the carburetor slide. Don't take the screw out of the carb though.
Now start the engine and keep it running by using the throttle grip. Try to keep it at near idle speed and manually keep it running at that speed.
Now turn the idle screw in untill you can hear it controlling the engine speed instead of you holding the throttle grip. Let go of the throttle grip and fine tune the idle screw untill the engine idles nicely.
This may take a few tries, but it really is easy to do.
Also with these cheap little engines it is common to have to re-adjust the idle speed regularly as they vibrate so much it will upset the screw position.