If using paint to touch up blush, dab a small bit on a q-tip. Paint it on with the q-tip, making sure to fade the edges.
Chalk pastels can also be used to achieve a similar effect. Scrape a bit of pink using an exacto knife to create powder. Then dab the powder with a q-tip and rub it in a circular motion onto the cheek.
Photos courtesy SourDoughStomper.
Photos courtesy Miss_Tuneful.
It can sometimes be difficult to mix paint colors just right and to keep a steady hand when painting. The more you practice the better you will get at this. You're also touching up a surface that has already been started for you, which makes it much easier! Once you've mixed your color to match the pony's eyes, touching up scratches and scuffs is relatively easy.
If your pony's eyes are so bad that you have to remove them completely, it's a good idea to mix your paint before you remove the eyes so that you have something to compare for a color match. If the eyes are so far gone that you can't tell their original color or what they looked like, try asking for closeup photos on a pony related Facebook group, the MLP Trading Post, or the MLP Arena. Other collectors are usually more than happy to help out.
Fine, soft, paint brushes tend to work well for detail work like this. You can seal and replace the shiny top coat on the eye with a gloss glaze or Mod Podge.
Photos courtesy Kanthaka.
The trick in choosing a brand of glitter or glitter paint ithat is both the same texture and color of the pony's original symbol. If you look closely, most glitter symbols are a mix of both silver and colored glitter. Look for glitters that describe their texture as "micro" or "ultra fine". After you've chosen your brand and color of glitter, paint the symbol with glue. Be sure to use a glue that won't run so that it holds the shape of the symbol, and that will dry completely clear. Aleen's Tacky Glue is a good choice. Sprinkle on your glitter and gently smoosh it down if needed to flatten it.
Acrylic paints work great for touching up and repainting smudged symbols. Mix in water to thin the paint. Once dry, the symbols can be sealed with a gloss glaze or Mod Podge.
I saw this mentioned at the Arena but I don't know where the information originally came from. Solarcolordust.com sells a powder that changes color when warmed. Their website shows it used in all sorts of things. It certainly seems to have potential for use with magic message pony symbols.
Molded symbols have a tendency to break off and are often lost, especially with the precious pocket ponies. If you can find someone to lend you a pony that still has the symbol you need to copy, you can potentially make a replacement using a casting kit. Another option, is to sculpt the missing accessory using Apoxie Sculpt. The same acrylic craft paints used for touching up symbols can be used to paint them, cover them with a glaze to reach your desired finish. There are often collectors who sell replacement parts. Ask on the MLP Restoration Tips & Tricks Facebook group to find out who currently has them available. Photos of Magic Hat courtesy BlackCurtains. Replacement bee photo courtesy Tory Y.
Courtesy MayCrestMom, these photos show the process for removing Princess Pony symbols. You can use metallic craft paint to fix up scuffed symbols.
Photos courtesy Starshinecustoms.
TinyShinyUnique created a nice color matching guide for Swarovski crystals. She provided these lovely photos and most of this information. Look for size SS12 or PP18.
Colors pictured (in order): Peridot, Amethyst, Light Rose, Light Sapphire, Rose, Sapphire.
Other colors, such as Ruby and Fushia, are close matches to some G2 ponies' eyes, while not exact. These size and color matches apply to adult G2 eyes. The size babies is PP14. If you know the names of good color matches for babies,please e-mail me! Also check out The Lavender Lagoon Eye Crystal Colour Guide.
Chipped jewels can be removed with a needle. Any super glue or craft glue of your choice can be used to hold the new jewels in place. TinyShinyUnique recommends pushing them into place using a nail stick. More info can be found in this thread: Online Reference for Matching G2 Crystals
Some collectors prefer to mix the glitter and glue together and then paint the mixture onto the symbol. Some also draw the symbols on with a silver glitter pen before gluing on the colored glitter, versus mixing silver and colored glitter together. Some use techniques such as painting the correct shape with acrylic sealer and sprinkling on the glitter before the sealer dries.
G2 - The jewels in G2 eyes are easier to replace. Swarovski crystals are expensive but have been reported to be an exact match.
Photos courtesy Lostpony.
This is what an original twinkle eye looks like with the original paint intact. Photo courtesy MysticIceDragon.
And this is a twinkle eye that has lost it's paint. Photo courtesy MLP Sunsparkle.
You can use a pearlizing medium to touch up and replace the pearly coat on ponies like the mail order pearlized babies. You will likely need to apply more than one layer to get the "shade" of pearliness just right. It's difficult to get it to look just like the original coat, especially if you're touching up scuffs versus doing a whole body repaint.