My Process
I frequently review and annotate wireframes for accessibility fixes at that level. The tracking tools (Jira, Azure DevOps, etc.) and design tools (Abstract, InVision, etc.) vary, but in general I use the same basic method.
Review story/acceptance criteria where available.
Context is key. By reviewing the story and its acceptance criteria, I have a better sense of what needs are being met with this specific effort.
Hold live UX office hours, individual review sessions, or request demos.
Documentation and asynchronous communication methods are great, but many times it is most effective to sit with someone, in-person or virtually, to come to a better understanding of how to make a design as accessible as it can be, while still fulfilling the purpose of the product or feature.
Accessibility Review
I will give each design a final pass before it is handed off for development. Here I look at all designs, regardless of prior collaboration, and make final annotations with information on behavior and states at the code level where I am able. If necessary, I will return a story/bug/feature to the designer with feedback for rework.
Wireframing
Occasionally I will take on the task of creating a wireframe for a story, especially if there is a very specific direction I feel a design needs to go to make it most accessible. I generally use Adobe XD, and have familiarity with the other user experience design tools.
In this flow, there was an initial design for adding and removing users from a list that was not as accessible as it could be. I created a design for a transferbox within a modal, that included all necessary alert messages and opportunities for user to commit their changes. Designed in Adobe XD and the prototype is housed on InVision.
Omar Bonilla 