First I will tell you that I am also not a body man or expert at painting.
I have been working on getting a Chevrolet Van ready for painting and I will tell you that to get anything even close to a nice paint job is a great deal of work!!!
I have now completed about 95% of the body work but to do it right takes many many hours of hard work and I am not yet to the painting stage.
What you did to your friends car is a real learning experience and the whole painting thing is very complicated between using the right paint, hardener, gun, pressures, and primers.
There are just so many different things that go into making the final product look great.
You did a very good job and you should be proud because for a first time job that looks good.