I'd disagree on the order and some of the substance.

You can't set the action unless the frets are right. Remove strings, and adjust truss rod (or use a jig and clamps) so that the neck is straight. Check with a straightedge (a pice of ally extrusion used to make flightcases is accurate enough, usually, and it has the advantage that you can cut it so that it just fits between the nut and the bridge plate). If that straight edge finishes up more than about 1mm below the top of the bridge plate, panic, because you need a neck set. Go to a professional (and a good one who will not take damaging short cuts like over-filing the middle frets).

If your straight edge sits nicely just on the top of the bridge plate all is well. Now you need a short straightedge that is very accurate. You may be able to make do with a bit of cut glass or a broken (straight edged) file. You may need more than one such becuase ideally you wnat it long enough to sit along three but not four frets. Stew-Mac sell a tool for this.

Work along the fretboard. If at any spot the straight edge sits up on the middle fret and rocks between the other two you have a high fret. It has to be fixed. Is the fret firmly down to the fretboard? If not you may be able to tap it in with a tiny hammer. do not go mad. If it won't stay in, you can try running a little very runny superglue in and carefully clamping. Don't forget to protect the back of the neck. This does however pose a problem for teh future when a refroet becomes necessary as although superglue will usually break cleanly to a sharp tap, it won't always.

Once all your frets are well seated, inspect for grooves.

If you are left with any high spots or low spots or grooves deep enough to cause unevenness in playing, you are going to ahve to dress the frets. Use as long a flat fine file as you can work with (or a long flat oilstone, or you can get away with emery cloth and some STRONG plate glass or a mirror but be careful not to break it) and smooth the frets up and down the neck until every single one shows it has been evenly kissed by the abrasive.

You should now crown the frets with a special tool, but if you can find one of those things with holes in that soldiers used to use to polish their brasses, or if you put two thickneses of electrical tape just next to each side of each fret to protect the fingerboard you can slightly crown the field angles with fine emery cloth or steel wool.

Now clean the fretboard and oil with lemon oil. Re-string guitar and proceed to neck relief.

There is only one correct neck relief: it's the curve such that the string always leaves the fret at the same angle. My first reaction is that this is geometrically impossible with the available tools - I have a horrible feeling it is going to be a parabola not a segment of a circle. But it can usually be approximated. Capo at first fret, and press string to fret at the neck/body join. Measure the clearance string to fret at the midpoint. You need feeler gauges for this. 0.25mm or a smidgeon less is good. Adjust with truss rod until right.

Now you can do the saddle. There are two issues - does the curvature follow the curvature of the frets? How high is the action? Capo at first fret. Using feeler gauges measure action at 12th or 14th fret. You probably want about 2.5mm on bass and about 1.7 treble. More if you play bluegrass with a 1mm pick, less if you do ethereal fingerstyle with your nails. But the first step is that you want the respective heights to reduce progressively and uniformly, so if you wanted 2.5 to 2.0 it would be bottom E 2.5, A 2.4, D 2.3 G 2.2 B 2.1 E 2.0. You can adjust the relative heights by tweaking each string aside and grooving the saddle. Write down what your measurements were! Don't worry at this stage if all are too high still, just get the progression right.

Now slacken strings and remove saddle. Freehand upside-down on sandpaper or emery cloth or a fine file, make a nice arc of the top of the saddle until your grooves all just disappear, and then barrel the top of the saddle. I am not going to talk about intonation (yet). Now on a flat turface like a mirror file the bottom of the saddle until you have removed the right amount so you have reduced and angled (sideways) the bottom of the saddle to give you your desired (say) 2.5 to 1.7.   NB, if you are installing an undersaddle bug you may need to chamfer the bottom of the saddle so it will sit correctly on the bug, and different makers ahve different views as to what is right.

Finally you can do the nut. There is only one right height for a nut slot. It is the height such that if you capo at the first fret and measure the clearnaces at teh second fret, then take the capo off and measure the clearances at the first fret, they should be the same. The nut slots should be done with special files with rounded edges so that the bottom of each slot is the same as the string that will sit in it. The angles of the nut slots are critical too, to avoid string grab when tuning. Both sideways and vertically the string should leave the nut slot at the same angle and if you are really OCDC you can barrel the slot vertically to reduce the break angle at the rear.

Of course, I can't actually DO it like a pro, but I understand the reasoning!