I have been off for an year or so and wanted to restart getting in to signature campaigns..
Welcome back to the forum, being a legendary rank member, I don't think you should be having an issue to how you could possibly start all over again, this is very simple and easy to achieve, get yourself active, make quality contributions, earn merits and later apply for a signature campaign if you qualify.
However I see many of the campaigners ask for merit points which one must acquire during last 120 days or so
You don't need to wait for that one twenty days, you can earn at least 5 merits to be able to participate in most signature campaigns.