I think I have 3 other spell damage trinket at this point other than the Darkmoon Card Vengeance Trinket which is always equipped. When getting up to the boss and you need an Extra boost of threat there is a few things you can do short of having a Destruction Potion (yet to find) available to use for kicks. So what's one of the things you can do. Well one of the things you can sometimes do in a 5 man Instance or Heroic is to switch trinkets and use the Scryer's Bloodgem Trinket from Scryers Revered if not there is one from HellFire Peninsular if you have that, name eludes me as WoW is down for maintenance. But I use the Scryer's Trinket. Pop Avenging Wrath (Wings) in between threat cycle right before you redo Holy Shield, Consecration and Judgement of SoR. Nice threat boost.
Always pop spell damage trinket before consecration and not during as it uses the spell damage you had before use when used in the ticks. Gives nice boost to threat with the spell damage trinket for 15 sec and cooldown last 1.5 min. Always use when cooldown is up. As to how to fit that into your threat cycle, everyone is different depending on their threat cycle but have Judgement of Crusader up when you use it for amplified holy damage. I always have the trinket with me, it may not always be equipped but always there to use if and when need.
Tanking Threat Cycle - Variable
Ready Seal of Crusader (*Depends if using SoR instead)
Holy Shield - Before boss
*Judge Crusader/SoR (Depends on first seal)
Pop Spell Dmg Trinket
Pop Avenging Wrath (Wings) - 30% boost to damage.
Judge SoR - When Ready
If you open with SoR for snap aggro threat on Boss the of course on next cycle Judge Crusader. If Crusader first then Judge and use SoR. All depends on how trigger happy your group is and up to your style. When need to use Judge Wisdom do so later on if need in threat cycle. However if i'm using the Spell Damage Trinket I will try to pop it and use Avenging Wrath both before I renew Holy Shield/Judgement or SoR, Consecration on the next cycle for greater threat boost when each comes up for use. But that's the basic idea with a spell damage trinket while tanking IF using one. However everyone playstyle can be different.
Related Info: Spell Rotations & AoE Threat @ Wolfbloods Writings