I have baked - with reasonable success - the brioche in The Bread Bible. Where I live, however, I cannot usually get instant yeast or dry yeast. I usually have to use fresh yeast. While I have mixed this with the dry ingredients after crumbling it as finely as possible, and while this does not seem to have caused any problems, I am sure that other techniques should probably be used when using fresh yeast. Any recommendations?

I went on a bread-making course last year in the UK where I live.  The course was with Richard Bertinet, a French baker who runs a cookery school in Bath, England. 
He prefers to use fresh yeast, although he does give instructions on how to convert the recipes to dried yeast if that is what you want to use.  His method is very simple, he just crumbles the fresh yeast into the flour as you would with dried yeast making sure not to get it near to the salt until the water goes in.  Of course you would need to be sure that your yeast is really fresh to use this method but I have used it with all of his recipes, Brioche included, and have been very pleased with the results.  In fact , I now prefer to use fresh yeast because I feel confident with getting good results.

FDALTON:
  Good morning & welcome to our baking forum. All I can say my friend is this “IF IT AIN"T BROKE…. DON’T FIX IT”
Here we generally get questions   LIKE:  WHY DID MY BAKED PRODUCT FAIL????...how do I fix it??? 

Good luck in your baking & enjoy your Brioche.

  ~FRESHKID.