I've discovered a four-part trick to easily convert regular muffin, quick bread and cake recipes:
1. Remove 1/3 of the required amount of regular all-purpose flour and substitute an all-purpose gluten free flour blend.
2. Add 1/4-1/2 tsp xanthan gum, if it's not already in your flour blend (I generally do 1/2 tsp per cup of flour)
3. Beat the batter to death (opposite of normal quick breads and muffins)
4. Let the batter stand for 30 minutes before filling muffin tins/cake pans
Mixing the batter up and letting it stand for half an hour allows the gluten free flours to absorb the liquid. As the flours are absorbing the liquid, the batter gets thicker, so it makes sense to reduce the amount of flour used. I've had success with this formula for numerous muffin recipes, for banana bread, pancakes and waffles. Also a chiffon cake, surprisingly. The baked food is noticeably less "dry/ grainy" than previously, and it doesn't dry out as quickly- lasting several days longer than usual.
These pancakes worked, these Cranberry Orange Muffins, (using 2/3 cup + 1/4 cup GF flour blend) and Blueberry or Chocolate Chip Muffins, (2/3 cup GF flour).
The secret seems to be reducing the flour, really beating the batter and then letting it rest for half an hour.