The standard way to reveal a line drawing is to add an open mask path precisely over each line in the order you want them revealed, then add Effect>Generate>Stroke. Depending on the drawing you'll want to set the effect to reveal original image or paint on transparent. Reveal original would be if your lines were on a transparent background. Paint On transparent would be if you wanted to use the layer with the masks to act as a track matte to reveal a copy of the blueprint below. Without seeing the blueprint I can't make a better suggestion.
Once you have all of your paths set up you set Stroke to use all masks, to stroke sequentially, then you animate the start or end point to reveal the lines.