i believe impermanence is in the small scope teachings of the lam rim.
just sharing my experience. i'm quite a newbie in engaged Buddhism. (in my country we all think we are Buddhist when we offer incense daily to the Buddha or Chenrezig
i thought that was all until i read the lam rim)
perhaps a short and effective way to contemplate on impermanence would be the "All compounded things are impermanent" from the four seals of Buddhism.
and also contemplate on the "Suffering of Change" which stated in sutra is “The suffering of change is that which is pleasant when arising, pleasant when remaining, but painful when ceasing.” this comes from the Three types of suffering.
we love to perceive things as permanent due to our attachment. however, through these contemplations or meditations(habituating the mind) above i believe one should be able to develop renunciation.
Just as the three poisons are "attachment" , "aversion" and "ignorance" we should use it to help us develop their "good"
counterparts "renunciation", "boddhicitta" and "emptiness/wisdom".