I completed my art exhibit by traveling back and forth one day. Redd's appearance is fixed but his inventory isn't, so you can buy a piece of art, travel to the next day, donate the art, go back one day, buy more art, etc., etc.
I also found this to be true. I'm still on the week of April 26th because I was busy with finals so I TT back to play this week, turns out I many things going on that week (moving villagers - island hopping LOL) so I'm still on April 30th and encountered Redd the same day (April 29th!) I plan on TT back and forth
I've seen him walking around and didnt care to see if the boat was there because he was walking around... when is he inside of his boat?? How am I supposed to know?