Hey, this is Pays164 and here's some tips on how to do 3-D graffiti. In my piece today, I only chose to use the E in Pay to make 3-D. First and foremost is finding your perspective in what direction you want that letter or letters to pop up. Me, I chose my E to straight drop. So my E is just rising up 3-Dimensionally, creating a flat E and then dropping my lines down in the direction I need.
Of course, 3-D graffiti gets a lot more technical than that. You can get different angles, different turns, but on the simple aspect just creating a certain drop and coming back through with the right type of shading, your 3-D piece will pop. Just come back through. Don't do too much overlapping with your second sketch so you don't get too lost in your piece.
Also, be careful not to layer that paint thick. Keep it thin and simple. You start getting drips at the beginning of the piece, they've already been layered, they're really going to layer in to the end product.