you will need:
3 TBSP hot water
1/4 tsp CMC powder or tylose powder
clean bottle with airtight lid
STEP 1: Put the hot water to the prepared bottle.
STEP 2: Pour in the CMC powder or Tylose powder.
STEP 3: Mix or shake well. You will see there would be gel-looking element inside. Don't worry it will disappear soon.
STEP 4: Let it cool overnight.
VOILA, you have a a bit thick and transparent-looking fondant glue.
I would suggest you put some amount in a smaller container when using it. Don't dunk in your paint brush to the mixture over and over again in order to avoid contamination and discoloration.