This is great progress! Unfortunately it's too late to sow any cover crops, though you can do so in spring (about March) if you prefer. Generally, cover crops for winter get sown in the September to mid-October timeframe so they have time to establish before the surface soil freezes and daylength becomes too short to support growth. Here is our information page about cover crops, if useful for future stages of the project: https://extension.umd.edu/resource/cover-crops

You can put down mulch instead, though, to limit erosion and to minimize weed seed colonization. Arborist wood chips are the best option of mulch type since they will be less prone to sliding down a hill (especially once wet from rain) and tend to be low-cost or even free. You could inquire with local tree-care companies about the availability of chips. This publication by Washington State University discusses this particular kind of mulch's benefits: https://rex.libraries.wsu.edu/esploro/outputs/report/Using-arborist-wood-chips-as-landscape/<personal data hidden>101842?institution=01ALLIANCE_WSU

For future weed removal efforts, you may find it easier or less labor-intensive to hire a herd of goats if there are no rare native or otherwise desirable plants in the zone they would browse. Given limited funds, this might be tricky, as costs may be higher than alternatives like hand tools, equipment, or herbicide (and certainly when compared to volunteer labor) but it may speed the removal of the bulk of the above-ground vegetation. Removal of regrowth should then be simpler with a team of volunteers, or the site could be browsed by the goats repeatedly to exhaust the weed bank a bit more before planting with native species.

Miri