I applied at a Med Spa and got the job as a regular esthetician, but I paid for myself to continue my education and took a certification in Oncology Esthetics. One of the reasons I was hired there was because I knew a lot of skin care lines from both going to different esthetics' schools plus I was a customer of esthetics before and I knew some medical lines. Good luck!
It depends on the spa. Experience and knowledge in peels and microderms will certainly help. Most places will train you on the other stuff if you have a good background on the basics. Like Nicole mentioned- the skincare knowledge is important too.