Hi
I used :
Coco coir 3 Parts
Fine Vermiculite 1 Part
Sieved MP Compost (any will do) 2 Parts
Soil 1 Part ( I don't always add this, have done without it before).
The compost and soil are used to make the mix stickier, coco coir on its own wouldn't work too well I imagine, also the compost helps with root strength I believe.
Just add water to make a wet mixture, too dry and it won't hold its shape, too wet and it will be too soggy. I was told the consistency is right that if thrown against a wall or something, it will stick to it. I just do it by trial and error, if you scrunch it in your hand and it holds shape, should be about right. Just do a trial run with the soil blocker to see if it works or not, then add water or compost/coir mix as required if it doesn't.
Re the plants I've grown in them, I've only done Sprouts, cabbage,broccoli, lettuce, and tomato. You are restricted by the size of your soil blocker, I think mine is 5cm, hence too small for bean seeds. I start peas straight in the ground, should imagine it would be ok for peas though, as they are smaller size. Just transfer them to 3 inch pots when they get big? Feel free to ask anything else.