No Mortar Snap Together Blocks!
Here is a Florida House at a corner showing 3 different ways to finish CMU
1) Stucco finish directly on the masonry
2) Adhered thin brick finish directly on masonry
3) Epoxy Paint where masonry running bond is visible.
Note - Mortar joints would not need to be filled in Case 1 and 2
A thick epoxy paint could fill the small 1/8" joints in Case 3