ADHD client who wants to manage time better but keeps procrastinating

My client is a college student who is diagnosed with ADHD, works best when working under pressure and he wants to get assignments done and without waiting for the last minute. I don’t have expertise in ADHD. We have gone over so many different strategies and yet he still winds up doing work last minute, albeit he’s doing satisfactory but could do better. He’s a smart kid but lacking in motivation. Today, I gave him idea of changing date of assignment on syllabus to a day earlier to trick himself to getting it done that day. Any other suggestions?? Does it just come down to discipline and simply getting it done?