Soak for a minimum of 2 hours, soaking it lesser time will make the vada/baray hard.
Whisk the batter really well, as it creates the air pockets and helps in making the vadas soft.
Soak the vadas in the water while they are still warm. If you soak it after they cool down, they will be hard.
Add any tempering or spices of your choice.
If you don’t have a wet grinder, use a food processor for grinding the dal. Using a mixie or blender will not get the desired results.