what is the best contractual solution when you work with artits from overseas and you have a LLC ?

Hi I have my LLC who sign contract with american company. They want my expertise and some artists enroll by my LLC. But some of those artists are European. Consequently they can't do self-employment. And I don't want add an artist as a member of the LLC each time I have a project I created this kind of company to be sure I could work with artists from overseas, and this is the added value of my LLC. Right now, a cosmetic company in new york ask me to endorse an European artist. I have to sign papers, receive the salary on my professional bank account, make a deal with the artist to avoid tax or double tax after on this amount... And most of artists in the world are not self-employed. ... I m looking for the best contractual solution