Gratuitous passing advice
For me, the reason why I don't enter races is nothing to do with others being annoyed about me being on the course. I know how friendly they are. What I'm concerned about are those techy bits where I might need to step off or where I'll stack it (more likely) and slowing down the poor bugger behind me who is competitive. I don't want to be a disadvantage to others on the course.
I think that is a common concern for many women. I often feel more likely to stack if there is someone behind me too. In longer races (8hrs, 100km), if there are technical sections that I am worried about, particularly as I get tired, I get off and walk them. I don't want to stuff up my entire race at 80ks (or 7hrs) due to an unfortunate stack.
If it is any comfort (to anyone that feels this way) as you are probably aware, if you are in front, you have right of way and the person behind you should also know this. Slow riders are part of racing and competitive riders know this so they are the least of your worries. They are also very good at passing safely and quickly. Think of it this way, if you knock a few seconds of 5 competitive riders, it is still a level playing field. You get the rare individual who gets uptight and their main competition are usually their team mates. That is their problem, not yours.
As part of the pre-race briefing at our club races they provide a reminder about passing and stress that it should be an ongoing conversation. People have gone from being entirely civil to being unnervingly polite.
If I may offer some thoughts (and this does not oblige you in anyway to be hurried by other riders):
As soon as I feel someone coming up behind me I start talking to them and let them know that I will get them past when I feel safe.
If I am approaching a technical section and I dont feel safe with riders on my tail, I ask them to give me some space and let them know that I will get them past as soon as I can. I warn people if I think I might have to put my foot down through a technical section. If they have to put their foot down because I do, they are too close and that is their problem. If I warn them, they can drop back and, if I do dab a foot, I might be able to use that pause to get them past.
Another thing I used to do (if I had accumulated a few riders behind me) before a technical section, I would stop and let them pass so that I could get through that section and not feel hurried (but remember you are not obliged to stop).
I became quite accomplished at the one foot down pass where I would move to the edge, put one foot down without loosing much momentum and just keep going. Now I feel guilty whenever a novice does that for me before I have even asked if I may pass (and I thank them profusely).
If you are already going slowly, you probably don’t even need to slow down much for someone to get past.
Most race courses (particularly the large events) are designed to provide many passing opportunities because there will be a huge range of skill levels on course (send an email to the organiser if you are concerned before you enter). If it is in your area, ask about the technical sections that might be included. They might be keeping the exact course a secret until race day, but they might tell you some indicative trails/ sections to practice.
Try practicing riding at the edge of the track for a few metres (you don’t need to get right off it). Perhaps ask some skilled riders to practice passing with you, so you can get to know what it feels like outside of a race situation.
I think passing should be covered in any skills course, both being passed and passing.