I've used autoglym stuff on fabric hoods before, and it works a treat.
Try not to get the hood wet when you wash the car, then get the hoover out. give it a good going over with the hoover, with one of the attachments.
Then the autoglym stuff comes in two bottles, with a white sponge thing. You just spray on the cleaner and rub it in with the sponge. Then i found it would soap up, and rather than washing off with a hose, just to get a damp cloth and wipe it down with that. Then you spray the other stuff on which is a protector type stuff, which requires time to dry, so best to do it when you know its not going to rain for at least 24 hours to get the best results.
This process should see it looking like new.
You should only need to do that every so often, as usually just hoovering the hood should see it come up nicely, unless you get bird s**t on there or something, then clean it as above.