I concur with FROPVD ~ good advice there -- SALT is well-known to bring the blood pressure up, so a switch to WHOLE FOODS could help a lot and using spices and herbs as a salt substitute; and I would add CAFFEINE to that list. Get him to cut down how many coffees he drinks per day (I now only have 2 in the AM and only the odd one later); usually have tea which has less caffeine. I now add non-caffeine Chicory coffee with our regular coffee and that tastes great; can't even notice the difference.
STRESS is a big factor; needs to have some relaxing down time and can try any kind of soothing activities from music to massage, yoga or tai chi, etc. Whatever things that he finds peaceful, like fishing, etc.
Weightloss can help some people; but not everyone -- I have a friend that lost 50 lbs and still has high blood pressure, which can be hereditary ... so there is likely another cause (stress being the most common, if it isn't the diet). Try all these things first and see what happens ...