With regard to the breath, inhale pushes down,
exhale brings up, Bāhya Kumbhaka tightens.
Then total effect should be in the Apāna area,
therefore exhale and Bāhya Kumbhaka important.
With regard to directional breathing,
if no Mūla Bandha then exhale can start from the navel.
If Mūla Bandha held then exhale from the navel is not possible.

Link to Series: 108 Mudrā Practice Pointers

Āsana and Mudrā Glossary
– Grouped into Standing, Kneeling,
Lying, Inverted, Backbend, Seated & Sitting

Glossary of Prāṇāyāma & Bandha Practice Techniques
– Grouped into Primary, Secondary & Ancillary Techniques