Since you can resize the text buffer window you do not have to use dry erasers at all. Especially, with the 88 guns it is just a matter of knowing the range. It is a lot easier to kill the 88s with the M4 HE round than kill any gun with the 88. The problem with the M4's rockets is that they have a wide dispersion, so even if you are using the proper aiming point it will take more rockets than it would from an aircraft, for instance. The fastest way is the Sd.Kfz 251 with the Nebelwerfer 41 rockets, but no one wants to try it often enough to get good with it.