Best cheap plastic for DIY whiteboard
I have gone through many different versions of whiteboards; purchased and DIY.  Quickly, they all become terrible and the ink is difficult to erase.  I tried car wax to condition the plastic as well with little results.  I ended up stumbling upon a fantastic solution: I cam across some pieces of glass with rounded edges that were used for a shelving project.  There were about 2'x3' each.  Mounting these on the walls in our office was easy using some stylish brushed nickel mirror hangers.  They work amazing and I highly recommend seeking out glass as an alternative.