Viserys can only do so much immediately prior to battle without depleting his higher level spell slots at a critical time, but if he has enough time to rest and recover spells before they depart for Egypt, there is a lot of prepwork he can handle.
First step is to drop a Heal, Greater Restoration, and Regenerate on Michael. Sanya, too, if necessary.
Then Harry, Michael, and Sanya need
Renewal Pact and
Stalwart Pact placed on them. Might as well get Kincaid, too.
Then Viserys should use Ancestral Awakening to learn Extend Spell. That will let him put a
Greater Age Resistance spell on Michael and possibly Sanya if necessary which will last for 48 hours. They, along with Harry, should also get Extended Nine Lives spells. Mind Blanks for the Knights, too.
All of that is going to heavily strain Viserys' upper level spell slots, but that's fine, because now it's time to move on to lower level spells.
Among Viserys' Pages of Spell Knowledge are some pretty good spells I've been adding to his repertoire.
Harry, Kincaid, and the Knights should each get three
Create Magic Tattoo, each Extended, to provide them with a +2 Enhancement bonus to their three prime attributes. For the Knights and Kincaid I would assume Strength, Dexterity, and Constitution, while Harry would probably go for Constitution, Dexterity, and Wisdom (or whatever he needs most for his spellcasting). Each of those tattoos will be good for 48 hours. The caster level enhancement tattoo might or might not work for Harry.
Then Viserys starts using his
Quick Potion PoSK. Each will last 40 hours once Extended. Give everyone an emergency Cure Light Wounds potion, a False Life potion, an Ironskin potion, a See Invisibility potion, a Mirror Image potion, and a Heart of Water potion. Everything but CLW are pre-fight buffs, even Heart of Water, since it can be canceled to grant a Freedom of Movement effect.
Immediately prior to the fight, Viserys should cast Magic Army, since there will be lots of mortal assets helping out; +4 Enhancement bonuses on automatic weapons will be beautiful.
A Phantom Steed for each of them wouldn't be amiss, either, as they provide extreme mobility. Viserys should also be able to afford to use three or four 6th level spell slots of cast Greater Shadow Enchantment to place Grand Destiny spells on Harry, the Knights, and Kincaid.
Depending if you want Viserys to use Ancestral Awakening early, before seeing how it will be needed for the fight, using it to learn Heroism and Magic Vestment would be a good way to provide even more buffs for everyone. +5 Enhancement bonuses to AC are nice, and the +2 Morale bonus to attacks and saves wouldn't hurt, especially if a Moment of Greatness is added from Viserys' PoSK.
Whew...I might have gotten carried away a bit...
Anyway, Dresdenverse Wizards aren't the only guys who can do some neat shit with time to prepare.