So hopefully someone else chimes in, but sunshine #4 is an inert medium, mostly comprised of coco and peat. This means you would need to feed in it pretty much right away because it contains no nutrients of its own. But I've never tried transplanting from soil to coco so I can't really say how well it will work. I've gone the other way, from coco to soil, so I feel like it should work, but I think I'd try to shake off as much of the MG as possible before transplanting (but not if it means damaging the roots).
Keep in mind, growing in an inert medium like sunshine #4 means monitoring your pH much closer than in soil. Your shooting for 5.5 to 6.3, though my best results in coco were between 5.8 and 6.0.