This is what i would do..... you do whatever is easiest for you though!
1.) put a nice long piece of tape ABOVE & UNDER the emblems before removing them....so you have something to line them up with when putting them back on. Make sure the gap between the emblems and the tape is the same all the way across so your emblems go back on straight...
2.) take off the emblems by heating them evenly then go behind them with a piece of floss or fishing line....
3.) after their off get all the tape that is still on the car off by rubbing it with your finger, or by using goo-gone.... DONT POLISH IT or else when you go to put them back on they wont stick.
4.) get all or most of the tape off the back of the emblems.....sand them, paint them....clear them if u want.....then allow to dry obviously lol
5.) like someone else said GET THE 3M SKINNY DOUBLE SIDED TAPE. And have a razor blade handy so u can put the tape on the back of the emblems and cut the excess tape off. You may need some adhesion promotor, but u prob dont wanna spend all that money on that and use it once
so i would lightly sand the back of the emblems with some 400 or 600 grit so the tape has something to adhere to.
6.) put the emblems back on and make sure their evenly spaced on the top and bottom AND in between each letter.
What i like to do when i had to re-use emblems was to get a thick piece of tape and put the emblems on it face down....make sure their spaced good, then go and put them on the car.....when you put them on the first time dont press down really hard....set them on the car lightly so if u did mess up u can pull it back off without having to get behind it again with the floss.
Hope this helped.....good luck. Post pics when done.