1.
rain
Emphasize the retroflex /r/ by curling the tongue slightly back. Avoid tapping the tongue as in Spanish.
2.
around
Focus on maintaining the /r/ sound in the middle of the word without letting it become a tap.
3.
car
In American English, the /r/ is pronounced even at the end. Spanish speakers often drop or tap it—practice sustaining the /r/ sound.
4.
“The red car raced around the corner.”
Practice maintaining the /r/ sound in multiple positions within a sentence.
5.
Say “rrrrr” while holding the tongue bunched in the middle of the mouth.
Build muscle memory for the English /r/ articulation.