Square and flat will be the issue. If it is casted poorly and it isn't pretty much dead on, then it's junk. So when you get it try to make a cutting for an edge like the inside ledge of a picture frame. If you can easily work it to a CONSISTANT width, and depth, it's a keeper. Otherwise a router with a guide, or in a router table and a fence gets that done with minimal set up.
A lot will depend if you want to do it with hand tools, or burn electrons. For the jobs it does I don't find set up that difficult, or exhaustive that I do it by hand, rather I will set up a machine to get it done. It's only advantage is on a job you need to bring the tool to the work, like on a boat, cause lifting a boat onto a router table is a PIA. :-)