Hi all,
I have to agree with RVR800. The scan is paramount - nothing must be allowed to detract from it. As he implies, if you're scanning, then you're flying the aeroplane, comfortably hopefully, creating yourself more time for other tasks. If the scan breaks down, height, heading, speed etc. go to pot - now lots of mental effort is required to get things back on an even keel and so even less capacity is then available for the other tasks. Believe me, I've been there!
What I try is this, and granted it's not always possible. Try to keep your head still, looking straight ahead at the instruments. If you then need to do another task, say change a frequency, move your eyes, but not your head. This allows you to still scan through peripheral vision, to a degree. As someone else alluded to, do tasks a bit at a time returning to the scan between times. Remember, you have more time than you think, but you have to create it by management.
Knowing your aeroplane is a great help too, so that you can locate controls (carb. heat, flaps etc.) without having to look away from the scan to do so. This can be practiced on the ground, and for free!
Lastly, yes you're right: it is easier to preach all this than to practice it. It is hard work but it'll come. Best of luck.
Regards, GT.