On the outside mine are grey, but this still works fantastically. Use Burnt Linseed Oil and rub it on with a sponge. If the are badly faded it may take a few coats, however, lasts for agies.
Yes I looked at the hot air gun method and the result looks fantastic. I opted for linseed oil as I do not have a hot air gun and was worried about thinning the material the more it's used. also seemed to be more work.
some black liquid by CarPlan ( it's downstairs 'n can't remember the name ) ..
and Armor All .. .. mixed 50/50 ..
that's for the outside bits
for interior it be Armor All ..
for rubber surround seals .. including the exterior one between the main cab and rear hardtop
it's often a silicone spray .. i.e. to keep the rubber in good condition ..
Recently used the heat gun method followed by boiled linseed oil and was blown away. I have the dark grey trim and it looks as new. For the roof (3 door) I used gtechniq G4 a little bottle but you only need a quarter of it and the hard back looks great.