The Epic Bleed Solutions kit is easy to use. There are videos on YouTube to show you what to do. Shimano is oil based so if you spill it just wipe it off (best not get on the rotors or pads though).

I've done it with MTB brakes, if they're not bled properly it's obvious, do it again. I haven't died (yet)

Thanks. Epic Bleed were the kits I was looking at.

Right, I'll give it a go - what's the worst that can happen?

Will 100ml be enough to fill a whole system?

I'm not saying it isn't but might be a ball ache to only be able to partly do the fill/ bleed them have to hunt around shops/order the oil.

Anyway, good luck mate those kits are good and it's definitely do-able.

Unlike my Guides that are filled with paint stripper (effectively) mineral oil is much less stressful to work with if it gets messy.👍

That was one of my questions also. On the Epic website it says:

50ml of brake fluid is enough to perform a bleed on one set of cycle brakes (front and rear).

If the old brake fluid is particularly dirty or discoloured we recommend completely flushing out the old fluid and replacing with new. In which case you may need additional fluid.

Most of our bleed kits are supplied with 100ml bottles of brake fluid. This is enough to bleed a complete set of brakes 2-3 times.

... which doesn't really answer the question. A few old STW threads suggest that 100ml should easily suffice.

You can completely ruin your carpet, this I know and have to live with every day I walk past it.

How likely am I to a) end up with fluid all over the bike and floor, or
b) kill myself on the next steep hill?

It's impossible to bleed them without spilling a bit of fluid, at the very least. It only takes one mistake and you have fluid everywhere. Do it somewhere where it will be easy to clean up. Shimano fluid won't hurt your bike unless you get it on the brake rotors or pads.

The concept of bleeding is simple; you're just filling the system with fluid and getting all the air out. In practice, it can be fiddly. When you manage to get all the air out, the lever will have a solid feel. As long as you close the bleeder on the caliper and on the brake lever, fluid can't escape and air can't get in so they aren't going to suddenly fail as you're riding along.

However, making sure the system is properly filled, with no air in the reservoir, is important. If you have air in the reservoir, the brakes can go spongy if you turn the bike upside down. Generally, pumping the brakes then holding the lever for a few seconds, then releasing the lever will help the air escape back into the reservoir and get them working again, but it's much better to make sure they are properly filled in the first place.

it killed a patch of grass in my garden, my hands went green which freaked me out a bit 'till I realised it must have been the old discoloured fluid. scrub scrub scrub get this crap off my skin.

it killed a patch of grass in my garden, my hands went green which freaked me out a bit

Shimano fluid is mineral oil, so it requires the same precautions as other mineral oil. DOT fluid (used in most cars and some MTB brakes, such as Avids) is completely different. It will cause paint to peel if you don't wash it off with soap and water. Obviously, you need to wash it off your hands. I assume it will also kill grass, but haven't actually tested that.

'I accidentally let out all the fluid from my front brake'

As you got this far, you probably need to take the bike to a shop to finish the job, properly, safely, cleanly.

DOT4 will end up damaging every surface it gets onto.

Take a deep breath, relax and give it a go. It'll be sound and you'll feel great that you've learnt a new maintenance skill that will save you ££'s down the line.

To give it some balance though, sadly, you will certainly die - just probably not from this.

I chickened out. I took it to Evans as
A) it’s an Arkose, and
B) they said they’d take a look today.

They did it while I was waiting. The mechanic was a bit embarrassed as he had got the fluid in a few places it shouldn’t go, and they had no replacement pads, so they didn’t charge me. I had spare pads, so I took it home, cleaned it up and slipped them in.

My bike is now braking well, but squealing like a banshee. Should keep the pedestrians alert tomorrow on the way to work.

Cheers for all the advice. I’m going to get a kit and bleed them myself next time.