how can you join multiple masks into one???

I want to make a video of a self sketching pen as the uploaded video. To do that i thought of making a vector  of the  image that i want to sketch from illustrator and copy that as a mask to AE then use it to add stroke effect with reveal original image. Then use the mask path of same masks to move the pen layer so it writes along while moving the pen .but the only problem is since there are several maks i cant copy and paste mask path data to the position attribute  of the  pen layer. i mean i can but then i have to use key frames. but when there are lot of masks it is a pain in the neck !! so if there is a way that i can join all the mask into one mask then its an easy job!! Is  there any way you can join multiple masks or is there any other way to make this kind of a video??