You can DIY a paver or brick patio relatively easily with some research and a lot of labor :-) But unless you are used to working with concrete pours, I'd suggest you leave that to the professionals.

Concrete finishing is an art. I've been in construction my entire life and would never place concrete without a finisher. The guy has to note the weather and the slump before he starts troweling. Know anything about managing bleed water? Yeah, me neither. Real seat-of-the-pants stuff.

We do hundreds of yards of concrete per year - to be covered by brick or stone. When the concrete needs a finished surface, we still bring in a guy who just does finished concrete.

600 sq ft is about 7.5 cubic yards of concrete, or most of a full truck. In addition to the challenge of making it look awesome, the morning after you'll be aware of muscles you didn't know existed :)

I agree with others. Having to ask about DIY finishing 600 SF of concrete suggests that you are not likely to have the experience required to do it. Though nothing about it is particularly difficult, it's hard work (needs multiple people) and certain things must be done according to a time limit with no second chances. And it requires some special tools. For concrete, start with a different small project (50 S.F.) and work your way up.