I'll put this out there lol. I'm guilty. I sprayed my 55 that was already set up with fish in. It's not worth it and it was a HUGE pain! I'd go for the roller approach or do window film like when they tint windows.
I made such a mess... Fish were fine but the wife wasn't when she had black feet(oops) just when you think you've taped off enough area and the over spray will get everywhere TRUST me. Not worth it, coming from someone who did it.
"When creating an aqua scape, strive for the beauty of imperfection, as its art and there is no wrong or right, it's left open for interpretation" James Findley