Give him the Soothe bell, and then just walk. A lot. About 20-30K steps will do it. If you are using walking only, bring any eevees, happinys, chanseys or anything else that needs to like you before evolving along with you, saves time. Use the run north and south of Solacean (sp?) town - watch tv while holding up or down and occasionally change direction, you'll get there eventually. Keep checking them on the Poketch app (#6 I think) where you can tap them and see hearts. 2 big hearts means he's ready, so level him up during the day.
Alternatively you could feed him stat-altering vitamins and berries, level him up and give him massages, but I find the walking method - while it takes longer - is less hassle over all.