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It is said that when training it is best to utilise or mimic the conditions for which one is training. That way the training is fully appropriate to the desired outcome.
But this does not exclude other forms of training, which may also provide benefit.
Who is easier to help, the heavily defiled or the open-minded? Probably the open-minded, being less different from the helper. The heavily defiled are less cohesive so they need to be tackled on many more fronts and they will make little progress of their own.
Does helping the heavily defiled make it easier to help the open-minded? The heavily defiled can be really wacky making it challenging to pin them down to their problems. Beware, notions which one may assume one could lever from, may take no place in them. Training in this may make it easier to help open-minded people.
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