Notching is less a notch per se and more a cut. You’re not cutting a notch out.

Do it in max growth season. Use a sharp, clean blade (e.g. box knife). Make notch at slight downward angle. The notch should be about ⅓ the circumference and ¼ deep. Sap leakage is desired (means you went deep enough), but no deeper or you risk that branch falling over. Wipe up sap to discourage attracting pests. Don’t make too many notches at once.

Wait time for new bud varies; can be up to a month.