Is any special prep needed to use this over old bed liner?
Depending on the bedliner and condition, there may be. We don’t recommend applying over a drop in bedliner at all. Spray in bed liners which are in good condition and not peeling or delaminating in any way can be top coated successfully. Any chips or other irregularities can be patched by simply mixing a thick products using our powder additives and troweling over the area (not too thick, since you want it to have enough tack to stick). This does not need to cure before applying your final product. NOTE: The bedliner does need to be clean and free of any oil or wax residue just like any other surface.