You don’t read a virtual pin per say. You use it to set a value to a variable, then us that variable to do your comparison in your auto/manual control function.
for example:
int control;
BLYNK_WRITE(V2) {
control= param.asInt();
}
void automate()
{
if (control == 1)
{
//do this stuff
}
else if (control == 0)
{
//do this other stuff
}
}