Well, anything worth doing takes a bit of time to learn. You probably drive a car - remember how difficult your first lesson was? Riding an old motorcycle is no worse - and if you've ridden bikes before it's relatively easy.
Later classics, with a foot gearchange, may be somewhat confusing at first, especially if you ride modern bikes. There was never any agreement as to which side the gear lever was placed, or whether you moved the lever up to change up ("Up for Up") or up to change down ("Up for Down"). Of course, with a single bike it's not a problem, but if you plan to own a collection, maybe you should stick to earlier bikes with a hand gearchange!
Early machines are slightly harder to get used to, as they often have a lever throttle, and always use manual ignition advance/retard control. On an early low-powered machine, juggling three levers (throttle, air and ignition) to obtain the best engine response takes some skill and practice, but that just makes it more rewarding when you get the hang of it. On most machines with these three controls, only the throttle is used regularly; retard the ignition for starting and hard hill-climbing, close the air-lever for cold starting, otherwise forget them.
Training and practice are available, though not as widely as they might be. The Vintage MCC (see Contacts ) occasionally run training days where you get to ride several machines of varying ages, and local sections sometimes run "Ride a Bike" meetings. It really isn't that hard though - a couple of hours' practice in a quiet car-park or similar should have you ready for the road.