Combination attacks are found on page 80 of Martial Arts, and it is basically a rule for creating a custom special move that is basically an extension of the Rapid Strike mechanic using techniques. Our combination attack will use three different techniques to achieve this effect. The first technique is Sweep (Quarterstaff) presented on page 81. The second technique is Stamp Kick, on p. 80. The final technique is Targeted Attack (Kick/Skull), explained on p. 68.
Stamp Kick is -3 from Brawling. Let's say we have a Brawling skill of 14. That would make Stamp Kick, which is Brawling - 3 equal to 11.
The technique, Targeted Attack (Kick/Skull) is -7 from Brawling. We want to use it in conjunction with Stamp Kick, so that makes it -7 from a technique that is -3 from brawling. -7 + -3 is -10 So that means:
Targeted Attack (Stamp Kick/Skull) is Brawling - 10= 14 - 10 = 4.
We combine the 2 attacks and we add -6, a penalty that includes the -4 penalty for rapid strikes and some more for the usefulness of a combination attack.
An important note, if our hypothetical character had any of the typical Trained By a Master or Weapon Master techniques, the -6 penalty would become -3. Check Martial Arts, p. 88 for more information.
Combination( Sweep(Quarterstaff) + Targeted Attack(Stamp Kick/Skull)) -7 + -2
That is not "Negative seven plus negative two" at the end, by the way, it is "hyphen seven plus negative two." That is, the 7 comes from the Sweep (Quarterstaff) at 13, minus the 6 we get from the penalty of the combination attack. "-2" is similarly the 4 from Targeted Attack (Stamp Kick/Skull), minus 6 for the penalty of being a combination attack.
Combination( Sweep(Quarterstaff) + Targeted Attack(Stamp Kick/Skull)) 13+8
Because of the trickle down effect. If we max out the Stamp Kick technique, which costs 4 points, we also make the combination attack better. That makes Stamp Kick 3 skill levels higher, which makes the 8 in the combination attack also 3 levels higher, so it becomes:
Combination( Sweep(Quarterstaff) + Targeted Attack(Stamp Kick/Skull)) 13+11
We can also independently max out Sweep (Quarterstaff) by spending 4 points. If we spend that, Sweep (Quarterstaff) becomes a 16 just like the Quarterstaff skill, and once again the difference trickles down to the combination attack and we get:
Combination( Sweep(Quarterstaff) + Targeted Attack(Stamp Kick/Skull)) 16+11
I was told the original version was a little difficult to read, so I rewrote it a bit. I hope it is easier now.