" did clean off the grey lines like you said."
OK! Grey lines are taken care of and you now have a way to clean them off when they reappear.
"The issue is the beautiful wood deck of the Serenity has areas that look white and dry more like an abrasion, this mostly towards the edges of the deck, maybe the boom brushed over it. It is not a ding , looks more like an abrasion and it is not deep, just like skinning your knee. There are little lines on the deck that look like it in other places. Seems like wood that needs staining but what do I know."
Your analysis is probably "spot on".
The absolute best product to use would be some penetrating epoxy. The whiteness you are seeing is probably dryer areas in the wood where it did not soak up enough epoxy resin when your board was manufactured. It's very difficult to get a "perfect soak" over several pieces of very thin wood veneer (0.010 mm thick).
So, the penetrating epoxy is about the best you can get as it will be absorbed by the dryer areas in the wood veneer to the extent possible. Jamestown Dist. has this product as well as most boat supply shops.
West Systems also now markets a penetrating epoxy.
"Also I have trouble getting the fin out after sailing , should I send it a bit?"
Better to rub it with a bar of soap (as a lubricant). If it does not slide in and out easily, take a look at
the surfaces of the fin root when you have it out and you should see areas that are black and shiny.
Those are the tight areas. Better to use a smooth flat file and just work down the shiny spots.
What fin are you using? Still the wide 70 cm that came as OEM in the board.
Try a 60 cm vertical race fin sometime. You will love it with your 7.5 m2 rig. You aren't racing so the
absolute best upwind angle is not that important, plus you can rail the board (more controllably with the
60 cm) and get the nose of your Serenity to "bite" into the water and take you upwind extremely high and fast.
I took the Serenity out yesterday in the usual up and down wind here and while th others were stuck between the gusts, I was having great time and when the gust came just flying. I started enjoying the Serenity more than my large board.
If you have a place close to the water and don't have to transport the Serenity hull (car top or?) they are
really a fun board to sail.
I have lot's of fond memories of things that happened while sailing the Serenity.
"Thanks a lot"
You are most welcome!