To use or not use DOT5 fluid?

Well now, at first this was good news, as years ago I put a new MC and brake lines on my Scamp, and debated going DOT 3 or 5...I ended up going DOT 3 because I was seriously on a tight budget and I heard issues about DOT 5 being hard to bleed out bubbles and the pockets of water that get trapped. Seems that's still being debated.

Eventually I want to go to DOT 5. #1 reason? Won't eat paint. Although I have learned from experience that DOT 3 can't hurt paint that's 30-40 years old. :-) I was afraid I'd have to completely and thoroughly have the lines flushed...but if they mix and I can just pump out the DOT 3 as much as possible, then put in DOT 5 with some DOT 3 residue in there...that makes it easier.