I, too, usually just use the modifiers from SoHK. However, in a recent game, one of the characters was captured, while the remaining characters had an evil cowri (giant) prisoner. There was a race to determine who would crack first. In this case, we used opposed Self Control vs. Interrogation maneuvers. Thus, the interrogators had the advantage because they were using a skill bonus, while the prisoner could rely only on a skill category bonus.
Each "round" the interrogators would make an Interrogation maneuver and subtract the result of the defender's Self Control maneuver. If the result was positive, the interrogators gained that many "points" (i.e., the interrogators can never lose points). Once the interrogators had 200 points, the opponent cracked.
Fortunately for the PCs, the character that was captured was a warrior-priest with a huge Self Control bonus to fuel his love of Adrenal maneuvers. The PCs also made clever use of Culture Lore to determine how best to frighten the cowri, which provided a "subsequent maneuver" bonus ranging from +5 to +20.
As an aside, when interrogators use torture, I treat any bonus they receive as a penalty to Lie Perception. You can get the victim to speak, but he might just be telling you what you want to hear.