1.) ShareYourPaper.org (https://shareyourpaper.org/) automates making a journal article open access in accordance with journal policies - just paste in the DOI and follow the steps.
2.) Sherpa Romeo (https://v2.sherpa.ac.uk/romeo/) is an online database of academic journals' self-archiving policies. Authors can enter a journal's title and see which version of the pre or post-publication of the manuscript the journal permits them to make open access and when, such as uploading to the Brown Digital Repository (BDR) https://repository.library.brown.edu/studio/upload/.
3. Have a funder that requires Plan S open access? Use the Plan S-compliant journal finder: https://journalcheckertool.org/
3.) Questions about making a paper open access? Contact your librarian at email@example.com
Signing over copyright does not have to be all or nothing. Authors can ask their publisher for permission to retain certain rights before signing, such as using your own work for teaching purposes, or posting a pre-publication version of a work such as a final peer-reviewed manuscript or pre-peer reviewed manuscript (pre-print) on your personal website or depositing and disseminating the work for free, global access via your institution's online repository like the Brown Digital Repository (BDR), or creating a translation and/or derivative work in the future, among others. Contact firstname.lastname@example.org for assistance with understanding self-archiving conditions in a publication agreement.
The Scholarly Publishing and Academic Resources Coalition (SPARC) offers an online addendum form for authors to adapt and fill out to request certain permissions, such as the ability to self-archive a copy of their work on their personal websites and in their institution's repository, to send to journal/publishers before signing the author publication and copyright agreement. The online form is available for download from: https://sparcopen.org/wp-content/uploads/2016/01/Access-Reuse_Addendum.pdf. Authors receiving permission to self-archive can then deposit their manuscript in the BDR at the appointed time using the upload tool available at https://repository.library.brown.edu/studio/upload/ or by contacting the BDR at email@example.com for assistance.