This is not so much a how too, but an explaination of all factors involved to allow you to build teh best slider trigger pull to suit your personal needs.

many many many many factors are in volved.

and remember for every gain there is a loss when changing something on a cocker.

3 way:
soft soft 3 way, besales.. I like bombs better but not as easy to move the shaft but are shorter stroke :(

return spring:
an easier to move 3 way will allow a softer trigger return spring. longer with more coils (but very soft) makes for softer pull that will also return the trigger plate without trigger stick.

sear spring:
this is determined by lug to sear edge relationship, and hammer spring stiffness.

Lug:
the more rounded the lug, the stiffer the the sear spring needs to be to prevent the lug from sliping over the sear. the more squared the less stiff of a sear spring will be required. and the sear spring will make the trigger pull stiffer or softer just like the return spring will. and again longer with more coils is better. softer is going to make for a softer trigger pull.

sear:
if the sear is worn, rounded, or extremely slanted, a stiffer spring is needed to prevent the lug from slipping over. if the sear back is more vertical and less slanted you can use a lighter sear spring, but since it will catch the lug better it will require more force to slip the sear off the lug.

Hammer spring:
the stiffer the hammer spring the more pressure the lug will have against the sear and a stiffer sear spring is required to prefent lug/sear slippage. so for softest trigger pull the overall goal is lightest hammer spring but be able to maintain fps, but in many cases you'll loose efficiency.

lpr pressure:
the more psi from the lpr the stiffer the trigger and trigger sticks in the back position. Not enough and the marker will not cycle properly and 3 way leakage (some 3 ways can handle lower psi better than others). so just enough psi to fully cock durning rapid fire is the goal. if the hammer spring is real stiff then more psi is required to the ram to cock the hammer back, the result is a stiffer trigger.

lube:
some say no lube at all, I don't like grease at all, but I do use a light synthetic oil, if you play where it's dusty/sandy oil may not be a good idea. but we have lots of green grass here and it's not a major issue. but if my marker gets that dusty im tearing it down and cleaning it anyway :D
I do put some grease on the sear edge where the lug catches. Usually dow33. but no grease inside the frame.

Travel slack set screws:
most frames have 2 set screws to press the trigger plate snug against the bottom of the marker body. too tight and it binds. too loose and sloppy trigger. One screw is at the rear and the other at the front bottom of the trigger plate. Here's the key, most use standard set screws, but set screws that are flat on the tip will allow less friction against the plate. Then someone made brass flat tip screws that created even less friction. Then the best is the plastic (nylon I assume) flat tip screws. I know ANS did some of the brass and plastic tip screws.

trigger plate:
smooth on polish both sides, smooth and polish the entire top, smooth and polish the bottom that the set screws rub, smoother and polish the "ramp" where the sear rubs (polish the sear at this junction as well).

Polishing:
piece of glass and multiple grits of sandpaper. lay the sandpaper on the glass. some stick it to the glass in different ways. Metal paper is suggested because it can handle water. start with semi heavy sand paper (nothing that will leave sanding grooves) and rub the top, both sides and the bottom of the trigger plate on the different grits until super smoother but still dull. then I use a very soft cloth laid on a piece of low low profile carpet and metal polish to buff to a mirror shine. the carpet allows holds the cloth while allowing a slight give to contact all parts of the plate im polishing. I lay the cloth flat on the carpet with polish on it and rub the trigger plate/sear against it just like on the sandpaper.
nice high grade foam padded fingernail files work great for the "ramp" part of the trigger plate since you can't get to it well with a piece of sand paper.

Last words:
So as you can see it is a game of trial and error, many many hours of swapping and changing. As well as see that everyone has a somewhat of a different take on how to make it happen, which may be due to the fact that some like soft pulls and will allow a longer pull to obtain that softness. While some want a pull as short as possible and would be willing to have a bit stiffer trigger pull to achieve that shortness. Still yet, some want efficiency and once they have found the hammer/hammerspring/valve/valve spring combo to their liking they will work the frame to function with the lower internals. Some want to pinch paint and will let that be the driving factor (lowest cocking pressure possible).
On a pump this is much easier because there no cocking pressure involved. But a softer or stiffer pump stroke is a factor on a pump. :D

As I said, there is a trade off for every move you make on a cocker...

A great thanks goes out to vantrepes of moodypb.com for teaching us less wise and less experienced cocker lovers these lessons.. he will be missed.
Kmac