Lowering reactivity

Hi folks

Roo is very reactive to other dogs - unneutered makes especially.

Is there a way you have found to lower this reactivity? I'm thinking of trying to sort out some very very carefully managed socialisation but would appreciate any tips from you!

I am principally concerned for his calm and wellbeing - it can't be nice to go from 0 to 100 on the reaction scale... (There is one local dog he seems to hate above all others, and it gets a much more elevated reaction than other dogs ..)

Thanks!