Tips - switching from breastmilk to formula

Hi all, I head back to work in a few weeks and will most likely switch from exclusively breastfeeding to formula. My work days are just too busy and unpredictable to be pumping twice a day at work. I'm looking for tips on those who have done this. How long does it typically take for your breasts to dry up? And what's the best way to let them know to stop producing without getting a clogged duct? Has anyone been able to just breastfeed once in the morning and once at night? I'd ideally like to do that, just not sure how to get my supply there. I have also been pumping so have a good amount of frozen breastmilk. Any one have an idea on whether it's better to start with bottles that are combo breastmilk and formula or just give full breastmilk bottles til i run out of the frozen stash then start with formula? TIA! Hopefully this goes without saying but i don't need any opinions on breastfeed vs bottle fed. Thanks ladies!