Using exact match domain to help brand domain?

I manage an established local business website where the domain name is the business name - eg joebloggs.com

They have bought a generic domain name - eg plumberinbrighton.com - and they want to use it to improve seo, but want to keep joebloggs.com as their main address.

What is the best way to do that? I assume a simple redirect from generic to brand url will have little (or even adverse) effect?? How else can I can utilise the new domain?

Also, is there any advantage to having a subdomain on the main site using keywords - eg www.plumberinbrighton.joebloggs.com ??

Thanks.

If they redirect it google will only consider it one domain so seo would be a wash. The only way I know of is to develop the other domain with unique content and link back to the original domain. Don’t over do the links though or you risk google thinking its a doorway site made only for that purpose. If done sparingly there is prob no problem and you will get more traffic because of.