hi i do the same and have not long started in a hairdressers as self employed beautician and have also to contend with the fact that the last girl in here seemed to get the clients back up so reluctant to try me.
but what i did is give the hairdressers a free treatment to sample you and if they think you are good likely to talk you up to their clients, offer files and polishes as mentioned to clients with their hair developing. and also got leaflets distributed that had an advert on both sides, one hairdressing other beauty and went halfers on it to keep the cost down.
also the salon i work in has a computerised booking service that could send a text out to all clients saying you are here if thats possible.
but remeber it takes time to build up a clientelle, but i think always having a prescence in the salon as there is nothing worse than someone wanting an appointment and there s nobody there coz there only about when clients booked in, coz i dont know how many eyebrow waxes ive done just walked in or from someone getting there hair done, and i know its not much but then it gives you a chance to chat and let them know what else you offer.
but i have to say having a good relationship with the hairdressers and getting them to talk you up to their clients has been the most beneficial as the trust them and therefore trust their opinion if they were to recommend you and make them your walking advert.