[Wykkyd]

This is when I typically use the update tic. Update tic callbacks are "asynchronous". Your wait loop is "synchronous". It technically causes more churn, and locks the process until that loop ends.

local firstRunCalled = false
local firstRunComplete = false
local callFirst = function(...)
    -- do whatever has to happen first
    firstRunComplete = true
end
local callSecond = function()
    -- do your second thing here
end
local mainFunction = function(eventType,...)
    if firstRunCalled and eventType ~= nil then return end 
        -- eventType having a value means it came from the event handler, not our update tic. 
        -- Since we're already running, skip it until last pass completes
    if not firstRunCalled and eventType == nil then return end
        -- standard update tic but we're not processing
        -- so kick us out
    if not firstRunCalled then
        firstRunCalled = true
        firstRunComplete = false
        callFirst( ... )
    end
    if not firstRunComplete then return end
        -- kick us out if it isn't complete yet
    firstRunCalled = false
    callSecond()
end
EVENT_MANAGER:RegisterForUpdate("myaddon_mainfunction_updatetic", 100, mainFunction)
EVENT_MANAGER:RegisterForEvent( "myaddon_mainfunction_eventwatch", EVENT_WHATEVER, mainFunction)

Something like that, perhaps. Sorry, this is off the top of my head. Basically hook your mainFunction into both the event, and the update callback.