First
Sampling Technique generally means whole sampling process from start till end. 
Sampling Methods means simple random, stratified random, cluster , interval based etc, rarely sometime author may refer them as sampling technique 
you can keep in mind general meaning, context and complete statement will make it clear what they want to say
Second
Audit procedures means test of controls and substantive procedures which are audit procedures to obtain audit evidence
Audit methods or audit technique means observation, inquiry , inspection etc
One more techniques / methods are used to execute audit procedure
 
sometimes audit procedures simply means all the work we do in audit from start till end again context and sentence will help you