Transfering/merging domains while minimizing...

I need to learn the best way to transfer one domain to another with a minimal loss in search engine visibility and traffic created from good visibility.  Google suggests using a 301 Redirect, but I've heard from sources that, while this absolutely works, it can take a significant amount of time for orgainc search traffic to return to its pre-switch levels (up to 6 months).

As our business model heavily depends upon driving site traffic, I need to minimize the time it takes for that traffic to return to normal levels; or better yet have the desired planned impact of improving ranking and visibility on SERP's.  Any thoughts on strategies outside a 301 Redirect?