As a mom of a bullied child, how much do you get directly involved in helping him fight against bullying?

As much as is safe as possible before it gets too out of hand. Sometimes the support of others is what they need most.

I found it good that my mam just watched a bit a first and then went to school to see my teachers, I was always to scared to tell anyone but once my mam went in I found a teacher to help me and it was all better, bullying isn't a thing the child can do anything about really so I'd say get very involved

As parent it is really is hard to hear about your child getting bullied. If it's happening at a school then I think approaching school management would be a good start. If it is outside of a school you could try to talking to the other child's parent or provide your child tips to stand up for themselves. Standing up for yourself is as simple as not tolerating the bullying and telling the bully to stop. Bullies tend to pick on kids that they feel are easy targets. So by teaching your child to firmly tell the bully to stop.