I am a Filipino and I can do that. 'Coz all filipinos speaks Spanish in the old days.
Okay, let me teach you. You want to learn how to pronounce "perro" in Spanish but you always pronounce it as Pero, right?
Try pronouncing RR stronger like what the other people said.
It's just like you're playing a motorcycle toy, right? Try imagining it.
Rrrrrr!!! Am i correct?
If you get it, do it again, and again, and again until you can do it.
=D Hope it works.