First of all, what a beautiful boy!
Personally I’d say thinning shears would do wonders on longer fur and keeping the length equal without damaging the undercoat, thinners/chunkers are also much more forgiving when it comes to choppiness. For a sanitary trim, which I feel is what you’re getting at with wanting him clipped? That’s not as dramatic as a full coat shave.
Like you could easily scissor down the back end and tail to make it more tidy. But if you determined to clip, which for an older dog I can’t say I disagree with, right now I’m using these clippers from Amazon
Oneisall Clippers They are very much budget clippers, but have 2 speeds, has an adjustable blade length, are cordless and come with very sharp scissors. The lower speed gets through my terrier mix’s feathery coat. And the second, higher speed gets through my poodles puppy coat. The charge lasts awhile, they are very quiet as far as clippers go. The blade does get hot pretty quick using the higher speed, so if you’re going sani short, be mindful of that.
You’d probably need to use the higher speed to get through dense coat, I also recommend the same as the folks above to prep the coat well prior to clipping, a good bath, good conditioning and brush out will make clipping much easier and also remove some bulk.
But best of luck with your boy! <3