Hello, this is Dr. Bruce and I would like to help you with Finley.
I'm sorry to hear that he having this issue.
Based on what you describe, I would suspect that Finley ate something that was very bitter and irritating. It is very common to see a dog have a lot of phlegm and saliva when they ingest an irritant.
By far the best thing that you can do is to rinse the mouth out as soon as possible when this occurs. Use a garden hose and gently flush the mouth for 10-15 minutes to remove the offending material. It can also help to use a moist face cloth and wipe the gums off in case there is a chemical involved that sticks to the gums.
I would also give a dose of Benadryl (diphenhydramine) in case there is an allergic reaction as part of the problem. You can give 1 mg per pound, so if finley weighs 50 pounds, you can give him 50mg (usually 2 adult human tablets).
I would also give him a bath in case whatever he got into got onto his fur as well. We don't want him to continue to absorb it through the skin, or to lick himself and reingest the offending material.
If the vomiting continues, or Finley starts acting worse, then he would need to go to the vet immediately for evaluation and treatment.
I hope this helps and that Finley is doing better very soon. If you would like to continue this chat, please reply to this post, and I will get back to you as soon as possible.