There are 3 products that I have been using for lubrication of heli parts.

1) Man's best friend, WD40.

2) White lithium grease (yep, the same thing used in electronic appliances with small moving parts, like VCRs)

3) Tri-Flow lube

Typically I use the white lithium for lubing all bearings and other parts like the feathering shafts inside the head, during the initial builds of all helis.  I just apply a generous amount of the grease inside all bearings, with something like an ice-cream stick or something.  Unless I find a real need for it, I don't go back and apply the grease again periodically, mostly because of the routine maintenance described below.  If I have to re-grease, I just take enough of the heli apart to take the bearing out, and apply the white lithium grease again manually, and put the heli back together again.

For routine maintenance, after about every 8 to 10 flights, I spray some WD40 on the main shaft and the tail shaft, and wipe out the grime and dust with some tissue paper.  After that I apply the TriFlow lube to the main shaft and tail shaft.  I guess part of it does get into the bearings, and help keep the bearings run smooth, so periodic greasing of the bearings can be avoided (or, to be precise, delayed).