got lsf bad.made a brew in a bucket follwed instruction, bubbled up nicely,removed infected leaves, not much left on me plants, how long to work

It'll start preventing the spread straight away. But you'll need to re-apply to keep it up. I do every four days when they're little (got it bad myself too). Need less as they get bigger and more established, I've found...

Totall agree DD.
Need it regular when small, I nearly lost a whole batch of cuts to LSF a couple of weeks ago, been applying essence every 5 days and now showing good healthy new growth on all of them, roots doing better, saved a whole crop for me, but do need to be very regular, and diligent with pruning off infected growth,,,,

Monk...x

Good point to make about the pruning of infected bits and they are much harder to keep going when they're still small aren't they? Perseverance and don't lose hope, mine root fine in cubes in the propagator but once out are slow to start the vigorus shooting you would expect and show signs of the fungus. For me then is the battle and the time to stay on top of the essence and pruning. It seems for a while I am taking off lower leaves at the rate higher ones appear and they look a bit bare. I use OT's suggestion of cutting the infected bit off the leaf and about 5 mm higher than the infection (if possible) and leave any green bits on. This is the slow part for me. After a while the spread will slow to a stop and I find myself taking less and less off, and start to see new healthy growth which speeds up to an expected rate. Don't lose hope through the slow bit.
Essence is the ONLY thing that is letting me keep growing these days - took me six months of trying everything else before discovering it.
Have two plants that are the survivors left from 8 cuttings I was losing when I found essence. They are now 5 weeks into flower and looking as healthy as anything I've grown in the past (if not more). And I'm expecting about four-ish off each. Have a tray of eight cuts to follow that are now past the slow point I mentioned earlier and showing happy new growth. And I have had real bad problems with LSF.
Good luck - also don't dilute down the essence if you have it real bad. The more concentrated the better (I'm talking about the essence powder here not the catalyst that you add - I use 1ml to a max of 1.5 ml/ltr not 3 as directed). And get some bio-wetter too to help the coverage...

cheers guys, just looks like i have to be pateint, strange thing is i have 3 strains in my mum room and its onlty the blue cheese to be infected. to keep the lsf at bay does this mean traeting all the through to harvest or just till the lsf is gone?

I'd spray them all to start with then re-application as needed. As said earlier, this seems to be needed less as they get older.
Mine were sprayed until maybe two weeks into flower then seemed to be holding their own since then. Would do as required from around then on...