I use frontline spray because I can do all 14 chis with one bottle
I always spray them outside and leave them to run around to dry. Their coats(all smooth) feel a bit coarse when they've just been done but soon return to normal.
I like the fact it can be used on young pups so I feel it is safe to use on Chis.
We have never had a problem with fleas & I treat my dogs as a precaution, I'm a dog groomer & don't want to bring 'visitors' home with me.
I think both spray & spot on are ok it's just a matter of preference.