Can't get old bundle format to work

[ackammawork]

Now that ---new-bundle-format is true by default, my vex document attestations are using the OCI 1.1 referrers API. The issue is I want trivy to be able to detect my attached vex document from my registry using trivy image <image> --vex oci and that only seems to work with the older tagging method. So I'm trying to set --new-bundle-format=false and I can't seem to get it to work or understand what I need to do.

cosign attest --predicate oci.openvex.json --type openvex <IMAGE> --new-bundle-format=false
Error: must provide --new-bundle-format or --bundle where applicable with --signing-config or --use-signing-config
error during command execution: must provide --new-bundle-format or --bundle where applicable with --signing-config or --use-signing-config

I'm having trouble finding what I need to set for --signing-config and/or --use-signing-config and what these mean. I just want to use the old tagging method without having to install version 2.6.1.