Re: How and what to grind?
You need to make sure you have a smooth surface ( ie, no jagged pieces, or lumps ) so that you don't have problems with air bubbles. They can be hard enough to get out without having the glass try to "tent" itself over something that could have been ground down.
Make sure you don't get overly aggressive and grind the hull down to the gel coat though ( I managed to get close to that in a couple of places and had to reglass for strength )
Prep is the key to a good glass job...don't get lazy with it. If you plan out exactly what you are going to do with the glass/epoxy you plan to use, then you don't have to do the whole hull, but it stinks to have to break out the grinder again to finish something that you could have gotten out of the picture early in the process ( something I have to do, because I got lazy )
Don't forget...use a good dust mask ( not the paper type ), preferably half face with the HEPA filters-will cost about $35, but it's worth it for your health, and the replacement filters are cheap. Safety goggles for your eyes, and always buy a Tyvek suit larger than you think you need so that you have room to stoop and reach without exposing your skin ( full hood type ). Keeps tons of the glass dust away from you and your laundry machines.
You would also be well advised to try to "tent" your boat when grinding to keep the dust as localized as possible....it's not good for your health, it certainly isn't good for the health of your family and pets if it's flying all over the place.
