I just finished making the body of an electric guitar. I put on 6 coats of General Finishes arm-r-seal oil and urethane topcoat, gloss. The top part on the maple has some pretty bad streaks. Should I sand down until they come out and add another coat or should I do a wet sand with mineral spirits or mineral oil???

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From what I can see in the picture the streaks look like they are the wood and not in the finish. Lay the guitar flat with a light on the other side and see if the streaks are differences in the sheen of the finish. If not then its the wood grain and nothing you can do.

The picture doesn't show the streaks. It is definitely in the finish.

If the streaks are in the finish I would recommend wet sanding with water and applying another coat of finish. If you sprayed the finish chances are you didn't overlap the finish when you sprayed it. Spraying a finish is kind of like laying roofing shingles. Each row of spray is suppose to overlap the previous row half way. If you brushed it you may need to thin the finish a little and apply a wet coat and not overbrush it. The more you brush a finish adds air to it and sets up faster so it doesn't flow out as well as if you just applied it and left it.