Last few days I and my brother have been busy sanding the fairing compound on one side of the hull. I actually quite enjoy the sanding, I try to sand about 1,5 hour a day during lunch break and then it's a nice break from the office work.
I believe a trick for succesful/easy fairing is to put a sufficient thick layer of faring compound on to make sure you're able to sand the whole surface down to the required end result in one go. Much easier than to start with a thin layer, filling low spots, sanding, filling more low spots, etc...In my experience filling and sanding low spots is difficult without messing up the surrounding area which previously was fair.
Still a lot of sanding to do before this hull side is ready....
After a while I found myself only working with the four tools below: a bigish longboard (self made of cutof sandwich panel with paper glued with contact glue), a smaller and less wide longboard from a marine supplier shop, a brush and a drywall-trowel (hope that's the english word) to put the fairing compound on.
It's difficult to work on the concave part of the hull with the big(ger) longboard, so I ended up doing almost all of the sanding in that area with the small sanding board. As far as I can see now the result is still fair (enough), but maybe defects will show once some paint is on. Anyway, the bigger part of this hull area will never be seen once the boat is finished because it's under the wingnets.
The drywall trowel works really well: it's much thicker (stiffer!) than the normal iron squeeges and after some practice it's easy to put on a layer of fairing putty with a consistent thickness. I only use metal squeeges - they're easy to clean with just a paint heat gun and a scraper. On the first hull half I have used the 'ridge' method to put the fairing compound on, but on the other half I'll probably skip that step and just trowel a layer on.