I actually purchased that Abacus Paint program , and found its really useless , except to check your work, or line up letters or lines, other than that it limits ya on colors to use and Lettering fonts and won't always let ya SAVE the file back to the exact file format that it needs to be, ya have to use DXT Bitmap for that or Paint.net.
I mainly use PAINT SHOP PRO #9 for all my Repaints exteriors, interiors and re-shading cockpits.
sometimes I'll use Photo Shop
other times I use Paint.Net for pasting Textures to interiors or Logo's & emblems