How to tip: multiple makeup&hair artists

Hello!



I was starting to budget for vendor tips and got a little confused when it came to my make up and hair artists. I'll be having 2 artists come for the wedding to do both hair and makeup for myself and 5 others. The total quoted was $1300 (including travel fee).I was told that I should be tipping 15%-20% of the final price, which will be $195-$260, but do I just give that to the head artist as one envelope and they divide them themselves? Or should I be halving that and give it to them separately? All my other vendors are business owners or only one of them, so I'm not worried on how to tip, but when it comes to multiple, I didn't know the general rule!
Thanks so much in advance for any help!