I'd suggest either a little clean up of la beard with some baby wipes, seems laborious though .. wiping clean each strand; sooo my 2nd plan is dark grey and black eye shadows applied over the white make up, shade in the beard growth?
Just scoping of course lol as I am a laydee and have no such trouble
Experiment prior to la party event, then you should have it nailed in time.
Enjoy bro, hope you have a great time!