For my own training, which forms the basis of this article, I use heads from York Legacy Dumbbells, although nearly all of the methods can be applied with most other shapes. These are cast iron and have one fairly flat side and a flared side. I have 5 of these ranging from 12.5kg up to 22.5kg in 2.5kg increments, and before getting them had never touched, or even seen a Blob.
It felt most natural for me to place my 4 fingers on the flared side of the Blob and my thumb on the flat side. I soon realised this was in fact the 'easy' way of lifting them and it was more difficult and thus productive, to attempt all the lifts with my thumb on the flared side. Obviously at first it meant backing down to the smaller weights and building the strength back up and then my goal was always lifting the next weight up in this manner.
Note: Your Pinch strength is ultimately determined by your thumb strength.
If you combine Hand Grippers and Blockweights in the same session, always aim to do the Grippers first. You should find that some crushing done first will have far less effect on your pinch strength than Blockweights will have on your crushing strength should you do them first.
I currently train grip 2-3 times per week and alternate Blobs and Grippers each session. Sometimes a max gripper attempt is a good warmup for your Blobs. I find mixing up the exercises each session more productive than just doing, say, high volume singles. A sesion could include some max singles, 2 sets of passing from hand to hand and 3 timed holds with both hands on a reallly heavy blob.
These are merely suggestions, based on my own limited experience. As a complete novice I progressed from pinching a 12.5kg Legacy Blob in October 2008 to lifting a 22.5kg Legacy Blob (albeit with my thumb on the flat side) on January 1st 2009. For some further reading on Blockweights, please see Eric's article 'The way I trained to close the Ironmind #3 Gripper', and the section in John Brookfield's excellent book 'Mastery of Hand Strength' or any of the articles on www.straighttothebar.com.