It's a lot of tongue, but in a good way. French kissing my golden retriever is the best, very slobbery! Just make sure your dog's dental hygiene is good and you brush its teeth regularly
Joke aside, if your really that curious go and kiss a dog, odds are they will kiss back and then you'll know the answer to this. It may be weird or 'gross' to the average bloke who only swaps spit with humans but it won't get you in trouble if someone sees you doing it