I'm having a vastly difficult time with the pronunciation of the single 'r'. I know it's supposed to be pronounced as an alveolar tap/flap like 'tt' in 'butter' or 'dd' or 'ladder'. In between vowels like in para I have no problem doing this. Also no problem after certain consonants like in grande or pobre.
What messes me up - when r is before or after 'd' or 't' like in cortina, concierto, vidrio, verde I find I either have to add in an "uh" sound to make the transition from the tap to 'd' or 't' or vice versa, which makes me pronounce the word with an extra sound/syllable, or I just have to resort to pronouncing the 'r' like an English 'r'. I find it impossible to pronounce the correct way.
I've searched endlessly online, including this site and listened to dozens of speakers, and I can't find a satisfactory answer for how to approach this kind of sound. I've been stuck in this for the past few days. Please help.