I follow a similar recipe to Steve, probably since the genesis of our shared practice comes from the same source(Fiber-arts forum).
Though I always use urea in my direct application dye solution, I rarely if ever use it in in my LWI. With LWI I think I am less concerned if a speck or 2 of dye goes undissolved b/c I like the randomness of it in the final result.
I leanred recently from my dad(biochemist) and subsequently Paula that the isopropyl alcohol acts to seperate/encapsulate the individual alginate granules thus preventing them from clumping together once they hit water. I can only speculate(not being a biochemist myself) that being able to keep seperated from the other granules allows the alginate to more efficiently absorb and swell in the waterm, hence a shortr period of time to wait for the mixture to be ready.
All this being said...give different things a try and do what you like and suits you best. There is no "right way"
Kathy