Can I call on more that one spirit to assist with a working?

I am currently planning a working to get into my dream grad school program. I want to petition my ancestors for help, but I also feel drawn to use High John the Conquerer root (though he is somewhat new to me so I’m not sure if he’ll even say yes lol). Is there any kind of etiquette around only using one spirit for one working/issue, or have you found that spirits are fine with working together?