The moment you delegate, a second lawyer gains access to your client's confidences. That's not a reason to avoid delegation — it's a reason to do it deliberately. Confidentiality and conflicts are the two duties most easily mishandled when a case is shared, and the two most damaging to get wrong.
Run the conflict check first, share second
The order matters. A conflict check after material has been disclosed is closing the door after the fact. The performing lawyer should clear conflicts against the parties involved before they receive anything substantive.
Share on a need-to-know basis
A colleague covering a single hearing rarely needs the entire file. Send what the task requires and nothing more. Scoped disclosure is both better practice and easier to justify if anyone ever asks what was shared and why.
Put confidentiality in writing
An NDA between counsel isn't a sign of distrust; it's a record that both of you took the duty seriously. Built-in confidentiality terms — applied automatically to every engagement — remove the awkward "do we need to sign something?" conversation entirely.
Mind the client's consent
Depending on your jurisdiction and engagement terms, sharing a matter may require the client's informed consent. When in doubt, ask. Clients almost always say yes when the reason is "to get you qualified local representation."
Treated as a workflow rather than an afterthought, confidentiality and conflicts stop being a reason not to delegate and become simply the first two steps of doing it well.