Sounds like you already have a "main" domain, but you want to use extra domains to create additional traffic (via Google juice) to your main site.

I don't "develop" that many domains myself, but here is what I think:

I have had more success with the minisites, with most of the links forwarding to the main site. I often use DevHub.COM for this. But DevHub is a pain if you have many domains.

With the 301 it is harder to get metrics on how well the secondary domains are working. You have to rely on the analytics on the receiving site.

Here are a couple of other things I always do with a new domain:

1. Add the new domain to Google WebMaster tools. Don't forget to setup a sitemap.xml. This will definitely help with traffic.
2. Add the new domain to Bing WebMaster tools. Again, for traffic. Lately I've been getting some great Bing traffic, so definitely worth it.
3. Add some kind of analytics to the new domain. I use Google Analaytics.
4. Link to your new site from some other established sites that you have control of.
5. Blog and Tweet about your new site. If you have an established blog, like on Blogger.com, you will get into the Google index almost immediately.
6. Put Google Adsense on the site. I can't prove it, but it seems to me that if you have AdSense on a site, Google will index it faster. You can remove the Adsense once you've been indexed.