If it's Single Player or Battle, I just make everything piece-by-piece in JCS, often trying to give an area good eyecandy before moving on to the next piece of layout. If it's CTF or a complicated single player level (the frozen FSP level, for instance, with the three floors you could go up and down between), I'll sketch the mask outline in PSP7, then more or less transfer that over to JCS, and elaborate from there. Note that my CTF levels are not the highest quality ever.