Leading up to my section 4 exam, I would do all my practice tests using the LARE demo (calculator and whiteboard components).
When it came to exam time, I found that I didn't actually have to use the whiteboard component for any drawing. The questions I had relied more on understanding general graphic configurations and knowing what they represent (e.g. topographical indications of ridges, valleys, common road/pathways types, etc.). I didn't have to draw out/imagine any cross-sections either. I mostly used the whiteboard's text tool to note any numbers I had to keep in mind for calculations.
When it comes to the white board, you can just keep making new blank sheets (tabs with the + on the top) instead of spending time erasing what is on your current sheet.
Hope this helps and best of luck on your exam!