Odds in a multi-way pot

Hey guys. I understand odds calculations when I'm up against a single player: Put him on a range of hands, calculate my odds of winning against those hands, and compare them to the pot odds I'm getting (or giving). The mathematics is relatively straightforward to me, even when including implied odds. But I'm a little confused on what to do when up against multiple players. Specifically, what if I hold a marginal hand (e.g. KJ or Axs) and there are many limpers before me? After a certain amount of limpers, the pot odds I'm getting require me to call, right? When is that point? Are there any formulas that help me decide when the pot odds are "too enticing" for me and that I should also limp? If so, do my hole cards matter, or is it just kind of a random probability issue at this point?

OR: Do I try to put each player on a range of hands and calculate my odds of winning against each of them?

OR: I understand that at a 9 person table, as more players limp into the pot, my odds of winning approach 8:1. Should I use this limit as a guide, i.e. if pot odds approach 8:1, then I can limp in with any 2 cards?

Do implied odds become more important, or less?

At a certain point do I just play with ANYTHING, including trash?

Sorry for the long and wandering post. Any help on this would be greatly appreciated because it is giving me trouble when I encounter such situations. As of now, if there are 3 or more limpers to me, I will just limp with marginal hands, and continue to throw away trash. I just don't know if I'm leaking money this way or not.

Thanks.

PS -- I'm specifically referring to low-stakes NL cash games (0.15-0.25) and NL tourneys

I don't think preflop pot odds matter much at all in NL. The bets on later streets are so much bigger compared to the bets preflop, so implied odds and reverse implied odds are of bigger importance. The deeper the money is the more speculative hands you can play and the more careful you have to be with voulnerable hands. Don't go so far as to play any 2 though.