Honestly try to replicate just replicate the things he would do there at home. If you have a kennel, put the dog in there while you do stuff so it can get acquainted. Another example can be for nails — mess with your dogs nails at home and in passing. Let their feet, feel each of their toes, etc to desensitize them when the groomer does nail actually
A more short term solution can be using calming treats like cbd treats. You could do a more natural way by using organic lavender essential oil and dab a little on the inside tip of their ear and on the bottom of their paw pads of their back feet! We lavender many dogs at work and can be helpful to anxious dogs
And when drying them, it’s recommended to get a high velocity dryer — it will take you hours to use a regular hair dryer. Start with high velocity to blast off most of water and make mostly dry. After that get some light conditioning spray, spray lightly over coat, and then use hair dryer to dry while brushing UP. Brush down/with grain of the fur before washing, and brush up when using the hair dryer to get a fluffy look. It helps to hold some of the skin if it tugs too much on them!