you can look on the reranch site for fairly exhaustive, and somewhat exhausting, instructions on how to use spray cans of lacquer to finish guitar bodies. I have had some success and satisfaction using those methods. Just read it all a few times. Usually you don't have to grainfill pine, but you want to go to 220 to paint it probably. 150 will probably still show scratches. Use a block for sure. If you hand sanded all of that without a block, that will be kind of a mess. Usually you can use a sanding sealer and a block to figure you high spots and low spots, so you can get the whole thing flat before you prime it, or start with color coats or whatever you're doing. The better you prep it, the better it will turn out in the end, so take your time.