How about a play on words since Dog spelled backwards is God.  This will either be perceived and funny or offensive, so proceed with caution.  Success with this will be in how it is executed.

Of course, blogging and social media will play an important part of the overall marketing.

Your friend can join dog groups on Facebook and post a link to his blog about his product.

I'd suggest he get photos of his product on a variety of dogs, especially dogs whose fur contrasts with the product.  

Your friend can also consider getting a booth at arts and crafts faires held at Churches.  I'd guess they still hold events like that.  I made jewelry many years ago and sold my wares at arts and crafts faires including those held in Church parking lots.  Your friend can find someone with a non-competing items and share the cost of the booth space.

If he likes the idea of arts and crafts faires, he might want to focus his efforts on dog walk events.  He may even contact dog rescue organizations and offer to give a percentage of the profits of the sales at adoption events, etc. to the rescue group. 

Lots of pictures with cute dogs wearing them and post them to all the social media sites.  You Tube videos as well.  

Often we must "seed" whatever our idea is by giving some away or discounting. Pet items are a multi-billion dollar industry so wanting to pursue this is sound thinking. How about setting up in front of a pet store? Colonel Sanders used to knock on doors and offer to cook lunch or dinner for free. All he needed was the use of your kitchen. The rest is history made by him...Good luck and may it all make good sense Debbie Gartner 

Put the photo on Pinterest with a link to the Etsy store.  Do the same with other social media platforms.

I think I would wear one of these!

Post flyers on bulletins found on animal hospitals and clinics. Give a few samples away for Free for a video review that he can post on Youtube.

Picture...lots of pictures with well groomed beautiful dogs and cats.

Why would anyone buy it?

Impulse?
Obligation?
Conscience?
Vanity?

Can a GPS device be embedded?
Contact information?

Is this specific to a specific doggie religion or sect?

Developing a message Precedes marketing regardless of the cost.
THEN you set up a accounts on Esty and Amazon and have affiliates blog about it. 

This IS the right time. Christmas is coming and nobody knows what to get that dog. PPG has 26 article template that are worth the $36 entry fee.

market to dog groomers.... they see everyone's dog several times a year.... imprint groomer's company name and tel # on the cross!! and to vets.... 

Debbie,

I think you got some terrific answers.  Creativity abounds on Active Rain.  I hope your friend is very successful.  A

Church bulletins?

I'd find a really good blogger on pets etc and send some to her, Pinterest; Amazon just started it's own Etsy. 

Good morning Debbie Gartner calling your previos sales, your friends , your familie, the clients you did not do business with , cost just your time . have a great day

Social media and blogging at the cost of $0 is what I'd turn too. Get in contact with some blog sites that focus on dog related artciles, reviews or product and see if they would do a story on it. Pinterest comes to mind as a good place to share an item like that also with a link back to the etsy store.

Cute, hope these were a success.

Hi Debbie -- I like Gabe Sanders' answer -- there's nothing like a bunch of cute puppy/dog photos to capture attention.