If you are not familiar, there is a template to be found in missions/TEMPLATES/BAT_WAW_CHANNEL40MMT_Kent.mis that is an object created coastline and shire of Kent circa 1940 placed on the Channel40 map. While it has differences, the Channel40 map and the 352 have a degree of similarity. The template was built to be a copy/paste way to quickly build a scenario mission in that time/area. While the design work will no doubt NOT reflect your style of design it may have some use to quicken or help fill in areas on the 352 map. The harbors in the template were designed to have historical similarities to the real areas at the time.
The template mission can be opened in FMB (it may take a while to load, it is object heavy) and object groups (harbors, factories, rail terminals...etc) in the template can be selected, copied to clipboard. then open your 352 design map and paste them to the 352 map. They were designed to be freely used or modified to quicken or inspire mission design.