http://www.sjgames.com/gurps/faq/FAQ4-3.html#SS184.108.40.206 clarifies you can take bonuses to feint skill from Evaluate or Determined Attack
- Defensive feints applying to an entire turn's worth of attacks, rather than 1 attack, per Kromm in 2008: http://forums.sjgames.com/showthread.php?t=36363 "they apply to every attack that foe tries against you next turn. The rules use the term "attack roll," singular, simply because the combat system doesn't assume multiple attacks in general."
- most recent, rather than best, feint applies: http://forums.sjgames.com/showthread.php?t=139294&page=2 "Multiple feints never stack. Only the *most recent* (not *best,* but *most recent* . . . you can screw up a good feint with a bad one) feint counts."
- rapid strike -6 penalty being reduced to -3/-1 having either/both Weapons Master / Flurry of Blows http://forums.sjgames.com/showthread.php?t=146714
- shock and bad footing penalties apply http://forums.sjgames.com/showthread.php?p=459134
- can be done during a Dual Weapon Attack, per PK in 2010 http://forums.sjgames.com/showthread.php?t=68694 with 2 options "Feint as part of your DWA offers you the chance to trade a small defense penalty for a larger one, no change, or no penalty at all, depending on your relative skill and luck."
- the 2nd half of the DWA benefits from the feint (sequenced) INSTEAD of the -1 to defend against DWAs, since it is no longer technically a DWA
- the 2nd half only benefits from the guaranteed -1 (simultaneity) and not from the feint, which only applies to the next maneuver
- Feints and Deceptive Attacks stack http://forums.sjgames.com/showthread.php?t=20278 per Kromm in 2006
- On feints and what resists them, it's pretty simple: if the feint is based on a DX-based skill, mostly meaning combat skills, the resistance to that feint must allow a DX-based option, even if the feint moves the initial roll to a different attribute. So feints with things like Acrobatics, Dancing, and Karate can always be resisted by DX-based combat skill, even if the specific feint is, say, an IQ-based Acrobatics or Dancing roll to distract, or a ST-based Karate roll to beat.
- If, however, the feint is based on a non-DX-based skill that normally doesn't run up against the enemy's DX, it's fine to use the attribute that normally resists that skill as the basis for the resistance roll against the feint. So feints with Intimidation and Sex Appeal, since they're usually resisted by Will and not DX to begin with, might well be resisted by a Will-based skill roll.
- You can resist feints using your best Feint level, as always. However, you're limited to using the attribute base that that sort of feint normally allows to resist: DX for standard feints, DX or ST for beats, etc. So in your example, you'd start with Feint-18, but make a DX-based roll: 16 instead of 18.