Hi Chris
I use GarageBand on iPad and I take 2 approaches, depending on whether it’s a faster song with an even tempo or a slower song with more variation in tempo. Either way, the thing I would stress more than anything is that timing is critical, and makes the difference between something that sounds really good and something that sounds like a complete dog’s dinner!
Approach 1
For faster, even paced songs, I will usually lay down a rhythm track first. GarageBand does have a good number of preset rhythm tracks and loops you can use, but I love doing my own. Then I’ll work out a bass line and add that. I have a full size USB MIDI controller keyboard that I plug in to the iPad via a USB to iPad converter cable (pm me if you want to know details) and I play all the additional internal GarageBand instrument sounds (there are loads and most are pretty authentic) with this. Strings, piano, synth and other sounds can be added at this point too, or you can wait until after you’ve added your uke and voice track to the song. If you’re playing acoustic uke and singing, you can then plug in your external USB mic and play and sing along with what you’ve already recorded - I use my phone to video this part of the process and then later combine video and audio in iMovie (also on iPad). If you wish to add electric uke, that too can plug into the iPad using another type of converter cable (pm me for details of this too) and you can take advantage of a multitude of amp and effect settings within GarageBand! However, you can’t have a mic and electric uke plugged in at the same time as there’s only one input port, so the tracks for uke and voice would need to be recorded separately.
Approach 2
For slower songs with varied tempos, I’ll usually do the uke/voice part first, then add in GarageBand instrument sounds afterwards. Timing can be much trickier here as there’s no rhythm track to follow. You can, of course, add in rhythm afterwards too, but timing will be critical!
Using GarageBand on iPad is easier than it may seem from what I’ve written here - I’ve considered putting some kind of tutorial vid on YouTube outlining the above processes - is this something anyone would be interested in watching? (That said, there are plenty out there already, though I could of course tailor mine to what I do here on the Seasons). Or even arrange some kind of interactive Zoom session/s - would that be of interest?
Anyway, hope that helps in some way, Chris?