Yes you can thin with Mr. Color Leveling Thinner, Aqueous Acrylic Thinner or water. You can use hardware store l thinner as well but best to lay it down in thin coats (I assume you're airbrushing) and give it a minute between so the lacquer has a chance to flash off and evaporate before the next coat as it's much "hotter" than Leveling Thinner (which is also a lacquer) - it could literally melt your plastic model. Mr. Color Leveling Thinner isn't nearly as "hot" and is formulated to dry slower so your paint or primer has time to level out for a smoother finish.