I have that same mower for trimming too. Using it for trimming you probably wouldn't want a striping kit.
But you could use an operator controlled discharge chute (OCDC). Or you'll be trimming one bed and shooting clippings into another bed.
As for the rust, I'd recommend spraying some rust converter onto the metal before you paint. It'll stop the rust from popping back thru your paint. And it makes a good primer so your paint will stick better.
The Exmark makes an excellent trim mower. It moves so much air it sucks the grass under the deck if you get close to them. It cuts down on the need for line trimming.