What tempering process do you use when moulding chocolates
Either use both methods or just use the second step to maintain the temper/work-ability of your chocolate:

A) Use the double boiler method to start tempering your chocolate.

A bowl/pan of chocolate sitting above a pot of hot water - the water should not touch the bottom of the bowl/pan.

B) Dip the bottom of your tempered chocolate in hot water for a few seconds, scraping the base (and sides) of the bowl/pan, mixing it into the rest of the chocolate.  
You can repeat this step if the chocolate is not warm enough/cools down.

Of course you could look at investing in a chocolate melter.