How can we use demand plan functions without historical data?

Hello All, 

We are implementing LS NAV for our distribution and retail business. So far, we plan not to migrate our historical sales data from our existing system (ODOO ERP) to the new one, LS NAV.

What is the good practice for using demand plan and automatic replenishment functions at the earlier stage of the system use? Do they migrate some of the historical data or do they use manual replenishment functions for a while till they get sales data for some period of time? 

What would you suggest? 

Thank you very much.