No that's not how you do it. (I mean it is for regular Eclipse projects, but this is a Gradle project)
If you make a multi-build project you just have the mod project depend on the library project's output and have everything reobf on publish.
If you have every project separate you reobf with build, have the library publish to mavenLocal (or use a flatDir repo) and have your mod project get the library and fg.deobf() it