Our Monty was a struggle to trim. We started out by trimming one nail, and then playing tug with him until he calmed down. Then we'd trim the next nail. ...and yes, it could take up to an hour to trim his nails. We inspected his paws every two weeks using this same technique, whether or not he needed his nails trimmed. We are now down to 15 minutes to trim his nails. If we feel him tensing up, we stop and start playing with him again.
An important thing to note - inspect your clippers. If your dog is fighting you, it could be your blade is dull and is hurting him when you squeeze. If this seems to be the case, replace them or get the blade sharpened.