I am no expert but I have taken the plunge and thought I'd share a few of my mistakes and insights. Before you even start there are a few things you need to know. If you plan on using more than one color you need to have more than one screen ( one for each color). You are able to use M's coupons on the planten, inks and screens. So with 40% off coupons it's a great way to start. You should be able to use these on emulsion and registration film as well. You just can't use it on the machine.
Next lay your second film over the first while on your Yudu with the light on. Match up your marks and then glue your second design in place. If you match your film to the marks you made on the screen then when you burn your images everything should line up perfectly!
I have just a few thoughts on the emulsion film . I have used a spray bottle to wet the screen however it seems too wet. You need the screen just wet enough to have the emulsion stick. Think of it like a stamp, too wet and it won't stick or the emulsion runs off! ( not good! It will stain surfaces so make sure you cover your work area. I won't even tell you what happened. Let's just say lesson learned!!!) I found it much easier to just use a damp sponge and run it over screen front and back. The emulsion sticks just fine and takes less time to dry.