I recently accompanied a friend to be enrolled in the brown scapular devotion. The decon we approached said a brief blessing, mentioned the promises and sprinkled it with holy water. my question is wether or not this was a valid enrollment?
No, I don’t think it counts. A blessing is not the same as an enrollment. A deacon can bless objects, but I think only a priest can enroll you in the scapular. And there is a specific formula to be used. You should approach a priest for this. You might want to print out the words of enrollment ewtn.com/library/PRAYER/BRWNSCAP.TXT in case he is not familiar with them.
Here is a site that tells of the Brown Scapular enrollment.