We often digest PCR products with ExoSAP (a mixture of exonuclease 1 and Themosensitive alkaline phosphatase) to get rid of dNTPs and primers that are not completely eliminated by EtOH or PEG precipitation.
As written above using DNA spin purification kits Qiagen and others, also 23 years ago i have run the total PCR products on suitable agarose gel with low melting and concentration was adjusted based on fragment size, after cutting the fragment will be melt and extracted in Phenol/chloroform then precipitate using 1/10 volume 3M Na-acetate and 2.5 volume ETOH (96-98%) and wash in 70 % ETOH, dry dissolve in good quality H2O rather than TE buffer
Option 1. if you have a clean product without primer dimers and with if your gel quantitation suggests that you have >500ng/ul then just dilute 1:5 with water and then use 1uL of the diluted product as a sequencing tempate
Option 2. I you have weak amplification clean using a magnetic cleanup system for good recovery. the Life technologies chargeswitch PCR purification give 95% recovery and removes most primer dimers.
Option 3. if you have a dirty product (multiple bands/ large size primer dimers) then you need to run all your product on the gel, cut the band clean it up and sequence.
There are many PCR purification kits available. All of them working fine. The easiest and more convenient method is ExoSap treatment. This is a fast and a cheap method with no waste of the PCR product and all reactions could be done in a single tube. Go for it.