Having started a very successful business 12 years ago when my job was shipped to mexico (Thank You NAFTA!) I have found that you can spend $$$ advertising, but the best way to grow your business is word of mouth.
If you are to advertise or market, you have to reach your target audience for example, by posting here in the swap meet and on the main page of this site if not to expensive and other classic car sites.
A website is also a good idea as you have a advantage as you are providing a specific service for a specific market. You should have no trouble getting ranked high in the search engines if search engine optimization is done correctly on your website.
I would also suggest a "Refer a Friend" campaign with an incentive of a cash payout to the referrer and a discount to the friend/client. This helped me in the beginning. I made business cards with the "Refer a Friend" message on the back.
Go to all the car shows and body shops you can and hand out these Business Cards/"Refer a Friend" cards to everyone you see. If I am in the grocery store I will hand out a card to the person in front of me, behind me, and maybe even the cashier. If i'm in a public crapper and there is a guy in the next stall, I will throw a card underneath his stall to him. You get my point. I also give folks three or four cards and ask them to give them to their friends if they have any <-- amazingly they like that joke and laugh.
Always answer your phone no matter what. If you let a call go to voice mail because you are on the crapper, you probably lost a client. They are calling the next interior shop on the list. And yes, I answer my phone if I am on the crapper, in a attic, at a wedding, and while I am in a dentist chair getting a tooth pulled. If I miss a call I literally get sick to my stomach so it does't happen unless at church, at a funeral or special times with the wife (she put a stop to that).
I will say that it takes a good while to develop a reputation in any field. As you already know it doesn't happen over night.
If you have the patience and you are really good at what you do, the word will get out eventually and then you will be posting here that you can't keep up with the demand and everyone wants their interiors done in two days, and you can't find good help and so on and so on. I can't even go out to eat with the family sometimes without a line literally forming at my table with folks needing something or asking a question.
One more thing before I get off this soapbox. You can build a stellar reputation over years and years, but it only takes one bad decision to ruin it in seconds. Treat every client as if they were your family and do whatever it takes to make them happy, even if it means taking a little hit in your profit margin once in a while.
Hang in there, be patient, and do exceptional work. The clients will come.
Hope this helps a little.