Hi Shinu, You are making some pretty pieces. I decided to answer your e-mail with questions about shine, sanding, buffing here on the Forum. That way other people will be able to see what info you have already been given so they won't spend time duplicating it, but can perhaps add other different information.
As far as making a mechanical buffer from a sewing machine I'm sorry I can't help. I've never actually used a buffer, myself, because I prefer the control of hand buffing, but I think they are somewhat like an electric drill with a buffing pad wheel. I guess you could do a search for pictures of buffers and try to figure it out. The two seem so different. All I can offer is info on making the actual Buffing Pad for the wheels.
Carolyn Good with link to Desiree’s tute on making Dremel buffing pads
with a picture of the buffer set up.
Making buffing wheels from fiber
As far as sanding. We use a type of sandpaper that is black and in the USA called "Wet or Dry" sandpaper. It is used for auto body paint work and can often be purchased in auto parts stores. Here it is numbered from around 320 (very rough) up to 4000 (very fine). If a PC piece has been sufficiently smoothed prior to curing it should need only a small amount of sanding starting with #600 and then #1000. Some people continue sanding small amounts, using #2000 and #4000 for a few sanding passes as well. 400 is generally considered extremely rough for sanding PC. I would start with #600 for just a little bit of sanding and then onto #1000.
After sanding comes buffing. Many people use blue jeans material and some follow up that with muslin. All those aspects are covered here: URL to my PCC thread on hand-finishing off pieces (buffing-sanding) without varnishing so they are shiny, (but not as shiny as using a varnish) http://forums.delphiforums.com/polymerclay/messages?msg=64038.1
I use PREMO clay, a medium strength PC. I can quite easily HAND sand and HAND buff. If a piece is sufficiently smoothed before curing it really doesn't take a lot of sanding and buffing.
Below is the URL to information on using a specific water-based varnish "indoor use" varnish for applying to PC, but I have no idea if it can be purchased for you locally. The URL takes you to my topic post on purchasing and finishing/varnishing with Varathane using Sarajane's idea of slightly moistened makeup sponge ON PREMO clay (so it looks like super shiny glass, not plastic). Because Kato is hydrophobic these directions may not work for Kato. http://forums.delphiforums.com/polymerclay/messages?msg=64052.4
Some people use "Future" an acrylic floor polish to finish their PC pieces. It is inexpensive, though it can darken over time. Future floor wax is actually now called "Pledge with Future Shine". I have never used it, so find out how to use "Future" on PC you may need to do a search (Google, etc). Much info about "Future" at the following URL, including what it is called Internationally. In Turkey it is called “Pronto”. http://www.swannysmodels.com/TheCompleteFuture.html
<<and also i am having clear nail polish.>>
It's a good idea NOT TO USE NAIL POLISH on PC. Over time many kinds of nail polish can cause the PC piece to "melt" because of a chemical reaction. Sometimes you won't see it happen for 6-12 months, but the potential is there. In the early days of PC, a few pioneering artists used nail polish, only to find that after a year the pieces had "melted" and they lost all their early work.
I hope that helps a bit.
Anita in AZ