But seriously, yes it is a long and complicated process regardless of how you really get down to it.
I can say that generally I set the number of impulses to the max (16) and adjust timebar durationl as required. If you know the general tempo speed of your song, some basic math will get you your tempo speed.
Say you go the fastest possible which is time bar duration of 4 seconds and 16 impulses . Well 16 impulses in 4 seconds = .25 seconds per impulse. Seems super fast. BUT...
Some simple math tells us that in a minute period if each time bar is 4 seconds you will have ... 60 / 4 = 15 timebars. Now tempo is based on quarter notes, and this timebar has 16 impulses ... aka 1/16 notes.
So I generally split a timebar into TWO time measures on my sheet music which gives me easy access to 1/8th notes. So we take our 15 timebars and times them by TWO time measures to get 30. Tempo is based on 1/4 notes and our time measures can support 1/8th notes. So we can times 30 by 2 again to get ourselves up to the 1/4 note of a tempo ... so we see here that if we require 1/8th notes at any point in our song, the fastest tempo we can have with a metronome is 60 bpm.
Edit: Sorry, simple brain fart. Forgot to times by 2 again for the 1/4 note that a tempo is based on. So the tempo of the song set like this is actually 120 bpm.
AND that was just figuring out our tempo.
Some simple tips I can give you. Map out your music first. Take careful note of note lengths and rests, to figure out what note will go in what impulse. In each time bar .. measure 1 of sheet music goes into impulses 1-8, and measure 2 goes into impulses 9-16.
On sheet music, the C note that falls below the Treble staff and above the Bass cleff is called middle C. On a piano that middle C is Octave 4. I sometimes program it as Octave 5 because I dislike the midi sounds of the lower octaves on the music notes.
If you program a 1/4 note into impulse 1, then the next note will be at impulse 3 (unless it's a rest). If you program a half note at impulse 5, the next note will be impulse 9. If you program a whole note at impulse 1, then next note will be impulse 9.
Just remember each impulse (in this scenario) is a 1/8th note and space notes appropriately based on this knowledge.
If you can't read sheet music, the process will get longer. You can write out the notes on a Treble and Bass scale for easy access. Always watch for changes in what notes are flat or sharp. Look for tempo changes in the sheet music. Even watch for some sheet music where the Bass scale suddenly becomes a Treble scale for a few bars ... (GRRRR)
And figure out your best way to map the notes before hand so you can refer to your own diagram to know what notes at what octave to put into what impulse in which timebar. Good luck and may god have mercy on your soul.