Like any communications, it depends on your reader. if the person I'm signing to is well-steeped in ASL, I need to use very little fingerspelling--just for words needing emphasis or clarification, as Bottesini wrote.
If the reader mostly fingerspells, then I do too -- trying to spell at a speed he or she is comfortable with.
I hate to sound like a booring lanuage teacher, but the purpose of communications is so the receiver will understand what you mean. So writing, signing, or talking to confuse is an agenda other than communications, don't you think?