This is what you need. Not cheap, but cheaper than a powered router, and it won't take your finger off in a moment of inattention. Can use while drinking beer. I wouldn't buy the el cheapo version from China at Amazon, you need actual tool steel for the cutter and actual precision in manufacture. Lie-Nielsen probably sells one of these for twice or three times, but it'll be the most freaking beautiful hand tool you ever held. (I don't own any Lie-Nielsen tools. Maybe someday.) Key to using this tool is to shave a leetle bit at a time, at first just the tops of the bumps, then index down a couple thou and shave off bit more, till you get the floor of the cavity all smooth(ish).
Also, a tool like this you'll own the rest of your life.
www.leevalley.com
Also, a tool like this you'll own the rest of your life.
Veritas Miniature Router Plane - Lee Valley Tools
Discover the Veritas Miniature Router Plane. Buy this product now on our Lee Valley online store.