Hi Gray, great question, and great to hear a peer who had the privilege of this type of role! If it's my own design work I'll break handoff into two parts:

1) a checkpoint part-way through designing, to ensure I haven't missed anything and get someone with technical eyes to assess the solution.

2) a full handoff session to communicate nuances and ensure we're in alignment, before building.

For other designers in the team I'll trust and respect they have their own way, and only get involved if there's a larger miscommunication or frustration from either party.

Given I have an engineering background, I often received questions from Engineers seeking clarification how something should work, or if they found a difference between the design and the system guidelines.

From there it's a case of troubleshooting, involving design, engineering, and product in decisions (either a simple message to inform, or bringing them in for larger discussions), and making any updates or clarifications to the system itself.

If it's down to ability to implement, I also lent a hand to help overcome any technical difficulties or nuances that were difficult to code up. But, I would often check with their Tech Lead first before doing so if it was more than, say, 20 minutes of time.

There's even more to describe and nuances to share, but hope that gives you an idea!