Morris Minor Owners Club

I've just gotton my delivery of Oxalic acid from the UK and although it comes with mixing instructions and I know there has been some discussion about it here too, I just thought I'd post here seeking general advise on how to mix it and apply it etc. Just general hints, tips and advise would be great.

Disolve the crystals in warm water dont mix the whole lot at once just weigh an amount and add the relevant amount of water and apply with a brush.
Having used it in the past it takes a lot of applications to do anything and having recently tried Dennis`s reccommendation of neat fresh lemon juice I found that it worked better than the crystals.