If he is not keen on Recovery, have you considered feeding either mushed up pellets or a mix of recovery food and pellets? Please be aware that putting him on strict fibre and no veg is going to speed up his recovery/rebalancing of the guts; if you continue to feed veg, it is going to take a lot longer. Also make sure that you have some rough carboard or toilet roll inners for him. If you have got other healthy piggies, you can soak some fresh poos from them in a bit of water and syringe this to help re-introduce all the right things into his guts. it is a bit gross, but most ill and recovering piggies love it!
A lot of hand feeding is down to practice. The first time is usually the worst; a bit like learning how to cut nails! The trick is to not to let him wiggle out of it, get the syringe in behind the front teeth and not overfill it; one third to one half of a small 1 ml syringe is about one mouthful. Our hand feeding guide is showing you with pics how to best go about it.
https://www.theguineapigforum.co.uk/threads/complete-hand-feeding-guide.115359/
A lot of hand feeding is down to practice. The first time is usually the worst; a bit like learning how to cut nails! The trick is to not to let him wiggle out of it, get the syringe in behind the front teeth and not overfill it; one third to one half of a small 1 ml syringe is about one mouthful. Our hand feeding guide is showing you with pics how to best go about it.
https://www.theguineapigforum.co.uk/threads/complete-hand-feeding-guide.115359/