I guess you haven’t read any of the myriad of exercise selection and tricep threads in the t-cell and the bb forum?
First rule of elbow friendly tricep training: Use neoprene sleeves (tommy konos or some such).
Fairly elbow-friendly extensions variants:
-Pullover+Extensions / PJR’s (lie on bench or across bench, retract shoulder blades and don’t let the shoulder joints rise towards your ears while doing them… It’s not a lat pullover). Stop with upper arms at an incline.
Great for the long head due to the pullover part.
Doing these with a single DB is a bit hard on the wrists if you have small hands/short fingers (do them and you’ll know why), but the most elbow friendly extension variant ever.
EZ bar with narrow grip can be used as well.
-Scott Extensions / High Cable extensions facing away from the pulley (or kneeling with elbows on benches or some such)… You can do them with a semi-pullover motion with elbows in (more long head, easier on the elbows imo) or as a pure extension.
Watch Justin Harris do them on youtube as a pure extension with elbows out.
-Dead Stop Extensions. Upper arms stop at an incline. Lie on bench or ground, scapulae retracted (use 25 lb plates when doing those on the ground) and use an EZ or straight bar.
Bar rests on bench / plates on ground between reps, like a deadlift for the tris. Depending on possible ROM you can do a bit of a pullover motion again.
-Rolling DB Extensions, check maraudermeat’s youtube account (rawelite I think).
And don’t go too close to your max on any of these… They’re extensions after all.
As for tricep press variants…
-In-Human press in the smith but done with elbows mostly tucked, suicide grip and a slightly wider grip width. PL setup (shoulder blades etc), press towards feet as well as up, takes the shoulders out and engages long head more.
-Wide-Reverse-Grip Smith Press, watch Jason Wojo do them on youtube (chest/delt/tri DC workout, last exercise).
Again PL setup, press towards feet as well as up (on angled smiths, that means the bar physically travels towards your feet as you press it). Wide grip, but not a full reverse grip… Grip mostly with thumb and index finger and maybe middle finger, rest just hangs around. Bar lies in the crease the flesh of your hand makes.
-Close-Grip Press with elbows tucked and grip as wide as necessary, suicide grip too. PL setup and execution, though if your elbows are bothering you, you may just want to keep them tucked even on the positive instead of flaring them and pulling the bar “apart” with too much force.
Avoid dips, CGP with elbows flared and too narrow a grip, traditional skullcrushers (!) and DB extensions with upper arms perpendicular to floor… Well, any extension with upper arms perpendicular to the floor, really… Overhead extensions/french presses too.