What's the best workflow to record iPad synths (iElectribe/iMS-20/Animoog,etc) onto iOS Garageband?

Although I see this question addressed in bits and pieces across this forum and the web, there doesn't seem to be a coherent thread that covers

soup-to-nuts for the cleanest workflow to record tracks iPad synths I own--Animoog, iElectribe, iMS-20---onto iOS Garageband tracks while creating

a iOS GBsong.

I really don't want to record the tracks independently on the external iPad synths, export them out and reimport/paster them back into

Garageband....nor do I want to go outside the iPad over o my Mac....hoping I can stay within the iPad. Moreover, I'm crossing my fingers

and hoping someone can tell me I can lay tracks from the external iPad synths just like a normal multi-track layer using iOS Garageband's

own instruments. Can I?

(in case it isn't obvious, I'm using the word "external" synths to mean "external of Garageband"....not external of the iPad 2)

Can anyone help or share some ideas or links on how to do this cleanly?

Chaz😕