Well...I tried a skill challenge in my last session. It came as a surprise, but I decided that it would be a good chance to try this out (For some reason I'm slow on this subject). So my Warlord player was in a room with wounded/resting slaves, he decides that he, having helped 2 slaves earlier and now they follow him around helping for now, want more. He wants to convince the room of slaves to rise and help him fight off the guards. I tell him alright, this will be a skill challenge. I tell him the main Skills he will use are Bluff, Diplomacy, History, Insight, and i think I threw in Dungeoneering cause they were in a familiar dungeon. I told him to get 6 Successes DC 15 (before I found out that the DMG had been changed from Average/Normal DC 15 to 10, which I think is stupid easy) before 3 failures. I made it this difficult cause...they're slaves...and they havent eaten/rested for awhile, working hard, and just exhausted and hurt.
So, the Warlord has a +3 Bluff, +7 Dip, +0 Dungeon, +8 History, and +0 insight. Now I want to know if I did this right. He said he wanted to try Diplomacy first, he gave me a rousing speech (in character too!) and passed, then he tried to Bluff them, failed, now he has a -2 modifier to future bluff checks, tried diplomacy again, failed, no penalty yet, and then tried History, failed, making him lose the challenge and thus gain no supporters, if anything he made thigns worse for them (Mwahahaha!)
So my question is for a simple basic skill challenge (I excluded real details here, like what each would do and penalties if he failed etc...), did I do it right? And if not what did I do wrong.