chicken manure

Morning.  Yes 

It will evenly spread it for you... I do it to boost plants in the summer when they need a bit of TLC...

I don't think there's a hard and fast rule; it depends on which crop, how long it's in the ground, what sort of soil you have, and of course the weather.

My sandy soil leaches nutrients very quickly, especially in wet weather, so a quick crop like radish or lettuce would probably only get fed before sowing, whereas something like leeks would get at least 2 additional feeds throughout their long growing season.