If he has been ok with being picked up as an adult bun, he might let you pick him up too, but it can take a long time still. Adult bunnies tend to need a lot of time to learn to trust you completely, and letting oneself be picked up is the ultimate sign of trust, since in nature, nobody picks an adult bun up unless he’s planning to have the bun for dinner =/
You do have to pick him up for nail-trimming and health-checks though. It’s a million times easier if you have someone to help you, but if you haven’t, you haven’t. To cut a reluctant bunny’s nails you do a bunny- burrito, meaning you wrap the bun in a towel so it can’t hop away. If you are two people, the person holding the bun in his/her knee can cover the bun’s eyes with a hand or a piece of towel, that makes them less super-scared. But don’t expect him to like having his nails cut. You’ll need a gentle but firm hand and be prepared for twitches and kicks and other efforts at getting away.
Supporting the chest and butt and holding him close is good, esp if the bun can stick its head in the curve of your elbow, (between the elbow and your body). It makes them less scared if they can hide their head.