difrent pproducts have diffrent dose rates but as long as its got PRAZIQUANTEL or/and FENBENDAZOLE as the active ingredeents it will do the trick, dose rate is usual based off of the snakes wight, best way to administer is to enject the dose into a food item and feed it as per normal, worming sould be done ever 3 months as with any animal.
but read the instriuctions on the product you do decied to use,
David charges about $100 for a checkup and faecal exam. When I got a new snake checked earlier this year he suggested using a commercial wormer (ReptiWorm) which contains both of the drugs mentioned by pyrodarknessanny. His recommendation was worming with the recommended dose in two consecutive feeds, 10 - 14 days apart. He recommended worming twice a year. It is well worth seeing him, as he asks all about the environment your herps are in and is able to offer all-round advice.