Hello, before starting the engine try pulling the insulators on the leads back at the plug end to expose the metal connectors but leave them joined to the plugs. Start the car and grab one lead at a time at the thickest part of the insulator (to reduce chance of shock,dont worry it wont damage you) and gently disconnect it from the plug observing the spark arc upto 4-5 mm between the plug end and the lead, (as you lengthen the spark gap it draws more spark to that plug and this will often allow a plug to fire when it wont fire while connected), and then move it closer to the engine block and watch it arc to the block. repeat this listening to any change in the engine,(better with a higher,constant rpm),dial up the idle screw or just open the thottle at the linkage. This should isolate the problem cylinder and then just dry all the connections, then some water dispersant(wd-40,inox). If pain persists start changeing plugs around to isolate if it is spark supply or plug. N.B. if points or other electrical parts are a bit tired they will tend to give up when placed under a bit of extra strain like earthing though water etc.
Good luck, cheers
