100%!!!! I've had clients come to me after spray tans from other salons (I don't spray tan at my current place of work but I did for a couple of years..) and they have tan all around their ankles, finger nails, elbows etc etc.. when I spray tanned clients I always did it for them.. much quicker and easier to do it yourself than have to explain to them where to put the cream before you leave them to get changed or whatever. Literally takes a couple of seconds of your time but makes a HUGE difference to the result!
Important areas being: palms of hands, fingers, nails, knuckles, elbows, knees, back of ankles, heels and around the toenails too.
I just used Vaseline Aloe Vera cream (Im sure the non aloe vera one is fine too, I just like the smell lol). Its much cheaper than branded barrier creams, does a fantastic job, and isn't thick and oily like some creams, which I find a lot of clients don't like. Anyhow, I was the only person spray tanning at my previous salon and had lots of repeat business! Hope that helps!