FS 2002 aircraft repaint

I started this repaint many months ago,using PSP 7.0, lack of time had forced me to put it aside. I now would like to finish it but forgot how to make the colors transperant(in order to see rivets and skin joints,etc). The colors being used are orange, red and yellow(3 very dark colors). The next question that I have is how do you get the text to read correctly on both sides of fuselage, because the opposite side of fuselage is mirrored the text will also be mirrored. The last question that I have is how do you get plain white textures? What I mean by that is when you want to start a repaint,for example the landmark airlines 737, how do you removed the old textures so that the A/C is all white.Nick