The devilish charm of two types of gravel? Almost! (3-3)

'the devilish charm' is the definition.
'gri-gri' can be an answer for 'charm' (gri-gri is a kind of charm). I am unsure of the 'the devilish' bit.

'two types of gravel? almost' is the wordplay.
'two types of' becomes 'gri' (I am not sure about this - if you are sure you should believe this answer much more).
'gravel?' becomes 'grit' (I've seen this before).
'almost' means to remove the last letter (most of the word but not all of it).
'grit' with its last letter removed is 'gri'.
'gri'+'gri'='GRI-GRI'

'of' is the link.

Can you help me to learn more?