There are tricks to cut down on the grinding and finishing. Also the mess.
For the grinding, the best professional shops always cover the laminate with peel ply as the last step. This is wet out just like it was the last layer of fiberglass. When all is cured, it peels off the surface by hand. The advantage is since it is very fine grained cloth, it holds all the nubs and fishhooks down, smooths the edges, eliminates many of the fisheyes, etc. Well done, the result needs little or no finishing.
For mess, on small jobs, wet the cloth/mat/stitchply/whatever on a table, then move it to the job. Here's an example of the steps:
1) take a piece of 6 mil clear plastic, tape it over the repair. Use a sharpie to draw the outline of the piece of fiberglass you want, leaving a good border on the plastic.
2) set up a table and lay another 6 mil clear plastic piece on it, bigger than the repair.
3) cut a piece of fiberglass larger than the repair, put it on the plastic, mix some resin, pour it on the glass. Lay the first piece of plastic (with the outline) on top. Squeegee the resin around with a dry squeegee on top of the plastic. So far you haven't touched the resin. You can move resin to dry areas, or squeegee excess off to the side. If you don't have enough, lift the top plastic and pour some more resin on. Because you are rubbing on the plastic, not the glass, it won't tear apart and wrinkle up and get unruly.
4) When you have the glass wet out and squeegeed to a nice resin ratio (the minimum to still have it wet is usually preferred) take some metal scissors (no plastic handles) and cut out the shape you drew, right through both pieces of plastic and the wet glass. This is the first time you will need gloves, and maybe only one. Throw the scissors in the pan of acetone you have ready (no plastic handles....).
5) carry the piece to the repair location, flip it upside down and peel the bottom piece of plastic. Paint a thin coating of neat resin on the repair area, then slap the piece on the repair. Squeegee down if necessary or smooth by hand, then peel the top piece of plastic. If it is dripping with resin, you didn't get it dry enough in step 3-4. Repeat if more layers are necessary.
6) put peel ply over the whole thing and squeegee down, wetting a little more if necessary to get completely wet. Leave a couple of inches of dry peel ply hanging off it every direction.
7) Have a beer and let it go off. Peel the peel ply. Fish your scissors and squeegees out of the pan of acetone.
Many variations of this for various situations, for example you can wet out many layers (I've done 8 - 10 at a time), tapering to the outside, all at once on the first go. Do the first, peel up the top plastic and lay another on, etc.