If you are a slow rider then you should aim to yield ASAP, that's just the way racing works.
Also slow riders should be aware that faster riders may come past quite close in areas were the track is tight, as a lot of folk have raced XC, road, track etc. where racing closely is second nature.
Saying that the faster rider should aim to make their move cleanly and give a shout or guidance to smooth things for everyone. And being polite and saying 'thanks' never hurt anyone.