I adopted a Miniature Pinscher a month ago and I'm struggling with loose leash walking, any suggestions?

Hi Cindy,
About a month ago I adopted 10 month old intact male Min Pin. For the past month I have worked on just like trick training for fun and stuff like that to build a positive relationship. He is exceptionally food motivated and catches on to things very quickly. However I'm really struggling with loose lead walking (flat collar). He is very inquisitive and has a ton of energy. I don't have a large yard for him to run prior to working with him. Should I carry him to the park and exercise him on a long line (let him run) or try to insist he walks on a loose lead on the way over? I feel like I'm asking for a bit much (he has improved significantly in that he isn't acting like he was just shot out of a cannon anymore) but it's just very difficult to hold his attention for more than 30 seconds. Any suggestions? I'm not really used to this having had mostly Border Collies for the past 16 years.
He's a good guy, I'm just not really used to having a dog who is so small and so impulsive