·©Gerry Krueger  All rights reserved
  Notes:  The nice thing about acyrilics are they're very forgiving and mistakes can be painted right over.  Just think dots  and general shapes .  Thin your paints...I use just water and cheap paint.  Work in layers and let dry between layers.  I only said it was easy not quick.  
Painting buttons...

I'm going to try to explain this in a way that even non-painters can relate.  These are cheater roses. ..in no way meant to look like an actual rose....the same as fargo roses, spiders roses and other CQ roses...just enough to simulate a rose.  Like CQ  it just takes a little practice. You are not creating artistic wonders here just little buttons...Have fun!!

 I like to also use a liner 5/0 (on the left), a long thin brush, an angular 10/0 (in the middle) and a pointed brush called a spotter 000 (on the right)  If you're going to splurge on any one of these do it on the liner..

You can get by with just a spotter (tiny pointed brush used to make dots or spots hence name), even better a spotter and an angular. 
I

Paints:  To start I'd recommend   white, yellow,  blue, dark and light green,  dark pink or burgundy and a medium pink.  I just buy inexpensive acrylics at the craft store and often find bags of them at thrift stores.

Critical Preparation:  First glue the button to a scrap of felt.  This felt gives you a handle so you do not touch the button itself.  Once dry fill the holes  with any white putty from the hardware store. Optional  Sand the button lightly with extra fine sandpaper.  Now for the most important  prep step.  Brush a very thin layer of blue wash (blue paint mixed with water) over the button.  This must dry or cure.  I leave it sit overnight.  The wash gives the button a tooth or surface that makes painting so much easier and it is thin enough to let the luminosity of the button shine through
If you dip the angular brush in pink and then dip just the very tip in white and pull it sideways or in an arch, you get the same effect as you do an an ombre ribbon...a two-tone effect.  If you make a C  and then a backward C together you end up with something that looks like a little donut.  This is the hardest part and just takes practice.
Blank button with dried blue wash and all ready to paint
Take your burgundy  and make a blob just off center and add two "toes" above it.  Let dry.
Now take a lighter pink mixed with a little white on brush and make two upsidedown boobs at the tops of the blob.  This is easiest with the angular brush but a spotter with work also.
Now make two well rounded boobs at the bottom of the blob. The burgundy will show through from underneath and that is great.  It gives it depth. Let dry.
Now the most important element... the donut that you have been practicing.. .Right?  Put it in the middle of all those boobs.Let dry.

Take your angular OR your spotter and load it with some pink and white and make three upside down eyebrow just below the donut.  At the same time add a couple dots of pink and white to the "toes "  Let dry
Add a few leaves with your spotter and some stems.  Let dry.

The final steps are to make several thin lines of pink, then white, then burgundy right over the eyebrow.

Use your spotter to  make blue and white dots aound the rose and the buds.
I'd highly recommend watching the Margorie Harris little video and watch for the "donut"  She puts 3 boobs on top.  But notice how she does not hesitate  to go back in and touch up.  She doesn't use a blob but she's not trying to do it on a button.....   http://tinyurl.com/232jnq

Brushes:  Jerry's Artarama has a "mini" set of 4 brushes for $14.95. In fact they have many mini sets but this would be a good starter set at a good price.    

http://www.jerrysartarama.com/art-supply/catalogs/0064481000000

Another online source for good prices is Cheap Joes at www.cheapjoes.com.  The trouble with Cheap Joes is they have sooooooooo much stuff that unless you know what you're looking for it's very confusing and their site is not very helpful but prices are good.

Personally I just buy my brushes at Michaels (our local big chain craft store)  I do not buy expensive brushes because they need to be replaced quite often. 

When you're done, spray your button with about 6 thin coats of a clear acrylic coating.  I use Kryon's Crystal Clear.  Then I put a little "Antique Gold" Rub n Buff on the edge of the button for a finishing touch.  If I'm going to bead around the button I do it BEFORE I trim the felt.  If  you're not going to bead just trim the felt very close and taper cut under edge of button....

Buttons: You can paint on any smooth surfaced button...glass, plastic etc.  I prefer mother of pearl buttons. because I love their luminosity.  3/4 to 1" are the best size  but 11/4-1 1/2" are the easiest to start with. I also prefer a little thicker button with a self shank or metal shank but they are difficult to find and often expensive.  So I mostly use ones with holes and fill the holes with a white filler from the hardware store.  See prep info below...  

Some online sources include: 1" buttons and up $2.50 a dozen  http://buttons4u.com/Merchant2/merchant.mvc?
Also  very large ones available at   http://www.umei.com/buttons/mother-of-pearl-buttons-cat-bsp2001-6001.htm
 and  they are available on e-bay.

Roses look great painted on black buttons also....