FOR MX SWITCHES:
i would not lube where the spring touches the cap of the stem. there is no wear there. the spring also does not touch the stem in a typical actuation, i wouldn't bother with that either. in fact, the only place i recommend lub is the either the slider or the housing side of the points at which the slider touches the housing. for linear switches, i recommend lubricating the front of the slider as well, the tendrils that actuate the gold crosspoints (they are lubed from the factory but with a silicone lube that just does not last long enough or provide the lubridicity for really smooth actuation), and the arc-face of a linear switch. i do not recommend lube anywhere else in an MX switch.
FOR TOPRE SWITCHES:
for a topre spring, you want to lube in a circle around the slider. use a very thick lube (the thick formula works reasonably well). the idea is to attempt to fill the gaps between the slider faces. this will _increase_ the resistance of the slider, but decrease the noise in that resistance w/rt to displacement. it will feel stiffer but smoother.
there is one more place to lube a topre switch, but it must be done BEFORE the previous step. using a very thin lube and a small gauge needle, insert several drops into the slider. the goal is to get the lube to migrate to the PCB and elastomers. the reason to do this is to increase the seal between the elastomer bottom faces and the PCB. in my testing i've seen a slight difference between the elastomer membrane of a 55g topre switch and an unlubricated elastomer. it's very slight, but the tactile bump gets a little bit of a boost from the improved seal between the elastomer edges and the pcb.
the sliders make the most dramatic difference in a topre switch. for those, only thick formula makes any difference at all, and again, it increases the force required to actuate the switch but makes that force curve smoother. if you don't want that, don't lube your topre switches. i haven't found any other way to affect the action of a topre switch with lubricant.
