You will be more physically able to guide him down the steps than lift him up the steps.
Guide his nose with food, stopping at key locations coming out to have him slow his momentum.
Place the food in the vehicle (without the steps) as a lure to go in with you helping him from behind. Another approach is to place the food in the vehicle with the steps in place and then let him figure out how to get the food; be patient and only encourage him to get the food.
I’ve also seen bigger/longer dogs have a harder time placing their paws on closely spaced steps than smaller/shorter back dogs; our house stairs are steep with small treads and our bigger males have more issues than smaller females with the steps.
Our border collies can climb the trailer steps; jasper the greyhound could not (he had to jump in and out).
