In the video, I'm using a #4 tip. It's what I prefer. If you two-tone the icing or squirt some liquid food coloring in the bag it gives more of an appearance that the writing is thin or more delicate than it really is. If you're comfortable with using a #2 tip, it had better be pretty soupy icing or piping gel (especially if you write on cakes all day long) otherwise it won't flow easily and you'll have to squeeze so hard that your writing may look like you had the shakes! If the consistency is too stiff, you'll also be more likely to have problems with carpal tunnel syndrome in your wrists. I always write with slightly thinned buttercream (you can thin with water or piping gel), or you can use royal icing, or a combination of both. I don't think it much matters. Just use whatever you have that's already made and/or available (as long as there aren't any cake crumbs in it)! What I used in the video was whatever I could find in the fridge at the time! It's white buttercream, a little cream cheese frosting, and blue royal icing all still cold right out of the fridge! I just stirred it a bit and filled the bag. So see... you can use it even when it's a little stiffer than you'd like, just squeeze harder or let your hand help to soften it to room temperature!