Well the thing about fabric paint, is that it's meant to stay permanently on fabric, so getting it off is a little harder than the average paint stain.

You might want to try this method I found though, you'll need:
- Hand Sanitizer
- Rubbing Alcohol
- Q-tips
- Butter Knife

1. Mix some rubbing alcohol and hand sanitizer in equal parts.
2. Soak the ends of some Q-tips in the mixture for at least 15 seconds
3. Massage the area of the paint stains with the Q-tips, this should help weaken the bond the paint has with the fabric.
4. Use the butter knife to scrape off the paint.

Of course after that, rinse and wash the shirt to get the mixture off of it.

If that doesn't work, you could try the more creative approach and just paint the rest of the piece of clothing with fabric paint, to make it seem like there isn't a paint stain on it.

According to a few different sources, people have had success removing fabric paint from fabric using rubbing alcohol, either alone or in combination with a stain remover called Goo Gone.

Hairspray is also effective at removing paint from fabrics. I would soak the fabric in a rubbing alcohol/goo gone mixture, scrub it off, then spray it with hairspray before laundering to be sure it all came off. Do it as quickly as possible. The longer it dries, the more difficult it will be to remove.

You can buy Goo Gone at most mass merchandisers (like Wal-Mart or Target) or online from Amazon.
http://www.amazon.com/MAGIC-AMERICA-GG12-Goo-Gone/dp/B00006IBNJ

The best way to remove fabric paint depends entirely on whether it is oil-based
or water-based paint.

Oil based paint can only be removed with solvent or thinner for artist oil-based
paint. Any kind of clear oil can be rubbed into the spot to delay drying for a
few hours until solvent can be found. More instructions below.

Water-based fabric paint like Tri-chem Softly Flo or Cameo Decorative Paints can
be removed with water BEFORE the paint dries. Water-based fabric paints like
this quickly air cure. Hot or warm water will set fabric paint so use COLD
water to remove water-based fabric paint. The use of Tri-chem Softly Flo paint
Extender will help remove stubborn areas.

Here are the BEST basic instructions for removal:

1. Blot up as much of the paint as you can from the top. Remove as much as you
can with a paper towel, Kim wipe, or disposable napkin.

2. Place an absorbent material like a blotter directly over the spotted/stained
area and turn the fabric inside-out.

3. Apply the appropriate dissolver: Cold water for water-based paint or
solvent/thinner for oil-based paints with a stiff brush to the reverse side of
the fabric until you have "washed" the paint out of the fabric as much as possible.

4. Use the paint's Extender, if any, to remove the stubborn stuff.

5. For better results, if needed: Launder in soap and water, if possible, after
spot removal. Use Cold water for water-based paint and Hot water for oil-based
paints. Hand wash only the (formerly) stained areas or machine wash whole garment,
preferably. By using the reverse side of the fabric to apply dissolvers, you will
minimize the stain's fiber penetration.

from :http://www.fabricpaint.com/cameo/library/RemovingFabricPaint.txt

Fabric paint is usually a permanent paint on clothing, so it's likely you will not be able to remove it, or remove it completely. You can certainly try though, and there's nothing wrong with trying to remove it, yet I can't make any guarantees that the paint will be completely gone. I've found some things, you might want to try.

To start you will need the following:

1. Sponge or Scrub-Brush
2. Hairspray
3. Rubbing Alcohol
4. Cotton Swab
5. Butter Knife

What you could try:

1. Remove excess paint from fabric.
2. Dab the cotton swab with a little rubbing alcohol and blot the paint spot.
3. Spray hairspray on fabric.
4. Let hairspray sit for 1-2 minutes.
5. Use the butter knife to scrape off paint, and scrub gently with a sponge or scrub-brush on stain until paint is gone.
6. If paint is still there, you may have to reapply hairspray until paint is removed

After doing all this, you can also try purchasing some Goo Gone Spray Gel and spray it on, then finish up with washing the clothing.

While paint is still wet, apply rubbing alcohol or use wet wipes containing alcohol. (This may change the color of some fabrics; test on a hidden spot first.)

How do I remove paint from cloth after it dries? Sometimes fabric paint will peel off a fabric, depending on the fabric content. If it does not peel off, use acetone to remove, working on a test patch first.