Querying using Custom Fields

Hello,

I’m trying to find a solution for my website oldtenspeedgallery.com.
The issue is this:

I would like to use a non-tag non-category method (perhaps Custom Fields) to call up posts that share an attribute e.g., owner.

I understand that this what Tags and Categories are for, but I am already using them in another capacity.

An example:

In the past I have used the search to call posts that share non-tag and non-category content.

...speedgallery.com/?s=david+m

This works ok, but as my site has grown, it begins to pull non-relevant posts.

I would love the ability to assemble posts like so:

...speedgallery.com/?owner=david+m
or

...speedgallery.com/owner/david-m/

Can this be done using Custom Fields?

If so, how?

Thanks,

Cameron