I forgot – there a better way. You just use the MCDU itself – it calculates the V speeds for you.
Summary: After loading your Simbrief flight plan in (or enter it manually), and also load your block fuel and payload via the EFB, then make sure you have a Departure runway entered in MCDU’s Flight Plan page, then head to the Perf page, and enter a flap setting (eg. flaps 2). Then on the left click each V speed and they should populate.