I've done something sort of like this before so I'm sure my story gives you some insight.
I have a big forum that I do SEO for a lot and we were looking to rank our new sections for their respected keywords. Now, instead of fighting the big competitors we have by just building links, we decided to make multiple websites with the exactly keywords in the domain names. This way we ended up with 7 .com, exact match domain names. We filled these up with content and did some small SEO on them. After about two weeks they were all ranking in the top 3 for their keywords where my main site was nowhere to be found. We kept the sites there for about a month, and then 301'd them to our main site which led to our main site being in the top 5 after a week, and on rank 1 after three weeks and some extra linking.
When it comes to just having the domain names I wouldn't do it like that, I'd fill them up with content, do some quick link building for them, and then 301 them. This way you'll get their link juice and you don't have to do too much SEO for it.
Notes:
1. Get completely different hosts for the other domains
2. Make sure they're exact match, or at least close to it, otherwise it's not all that useful, they need to give you an advantage
3. Make sure the content you post on the sites is of high quality so you don't look spammy.
I'm not 100% if this is the best way to do it, but this is the way I did it and I had great success with it so I hope it helps!
