Handwriting - with a pen and wacom

Hi. Does anyone know a way to use a pen and wacom tablet in Aftereffects so you can just handwrite and it shows up writing over several seconds. I know there is the way where you go already written text with the pen tool making a mask but i really just want a quick dirty way. I haven't been able to figure it out in Aftereffects. I downloaded a screen capture program called Screenium and it works great in that except I can't figure out to make it have a transparent background - don't think it offers an alpha channel...
Anyone know? huh...? huh?