When squeezing out into the oil the heat should be high(hot enough)then reduce the flame(medium high not too low) for even crisp cooking.
If you cook it in high heat for all the time then the murukku will not be crisp.
Batter consistency should be correct otherwise whole thing will be spoiled.
If you don't want to add chillies you can skip adding it.
I felt that wet grinder is the best than using a mixie and taste also differs.
I have used star shaped nozzle you can use any type even a round one.