As far as the Pali is concerned, since I'm not an expert on Pali I've simply collected the translations that I have access to and given the caveat that this a verse section of a dense Sutta so any clarification would need an expert (not just a Pali dictionary...).
As to exactly how one maintains such mindfulness, that's more a question of meditative approach than Pali. Obviously it's a key question, but it might be better pursued in the Meditation forum, e.g. in threads such as:
The Practical Aspects of Establishing Mindfulnessviewtopic.php?f=33&t=7110