We thought about a dog trailer, but I didn’t want to tow the thing empty for 25 miles to put the bugger in it for the last few when he got tired.
For short road sections we use a walky dog boom like this
quick release boom when you get there, holds the hound behind your front wheel on either side.
Its not perfect, the shock absorber is rubbish but easily improved with some shockcord and you need to do it up pretty tight or an enthusiastic dog can twist it round the seatpost, get an extra mounting if you think you might need it as on its own p&p is high.