Lovingkindness Part Three

and on page Ninety-Two, Sayadaw suggests practicing lovingkindess up to the 'breaking down of barriers'.   How to do it? From Access to Insight: 

By order is meant visualizing objects, one after the other, by taking the path of least resistance, in a graduated sequence, which progressively widens the circle and therewith the mind itself. The Visuddhimagga is emphatic about this order. According to Acariya Buddhaghosa, one must start the meditation on metta by visualizing oneself, and thereafter a person for whom one has reverence, then one's dear ones, then neutral people, then hostile persons. As one radiates thoughts of love in this order, the mind breaks all barriers between oneself, a revered one, a dear one, a neutral one and a hostile one. Everyone comes to be looked upon equally with the eye of loving-kindness.
In the Visuddhimagga Acariya Buddhaghosa gives a very apt analogy for the breaking of the barriers: "Suppose bandits were to come to the meditator who is sitting in a place with a respected, a dear, a neutral, and a hostile or wicked person and demand, 'Friend, we want one of you for the purpose of offering human sacrifice.' If the meditator were to think, 'Let him take this one or that one,' he has not broken down the barriers. And even if he were to think, 'Let none of these be taken, but let them take me,' even then he has not broken down the barriers since he seeks his own harm, and metta meditation signifies the well-being of all. But when he does not see the need for anyone to be given to the bandits and impartially projects the thought of love towards all, including the bandits, it is then that he would break down the barriers."

Sayadaw also suggests practicing recollection of the Buddha, and of the foulness of the body.