Great game FE/SE, do you find yourself running backwards going "oh sh*t, oh sh*t" like Rincewind with rocket launcher. The bulls can be quite useful, you can get into all kinds of odd places by using them to your advantage. One bit where there is a lot of them, you can get hit by one and bumped up on top, then you can pick them off bullet by bullet.

Great!
If you like it, also buy Painkiller Black Edition and play it with two mods: Ordeal v2 plus Advanced Grapping Hook. Twice as fun! Sidestep exposes their ass for shotgun lead barrage.
And they are great canon-fodder, literally. Risky, but its usual situation. Problem is - they will try to predict where you move really close to when they make a jump.

Laser/Minigun or holding off grenade into them - as well as running around gathering the crowd, just to toss the grenade in middle of them.

In second encounter, flamethrower is very efficient against kleer.

Nothing beats the original.

How so? The tactic is the same as with the bulls but the only problem is that they come in numbers so you're often sidestepping into another kleen & kleer skeleton.

Because they come in numbers so you're often sidestepping into another kleen & kleer skeleton.

Bulls follow you a bit though, while the skeletons are more predictable because they just jump in the straight line.

Later in the game there are so many skeletons after you though that merely sidestepping and shooting at their back is not enough, but you have to keep running backwards in circles and shooting like crazy...

When you hear it jump, instantly hold keys for opposite different direction+away from the source of sound.

but at that point you might already have the cannon weapon which is great for skeleton hordes

I keep thinking about that scene near the very end of the first game, where you are locked into an arena and enemies (including skeletons) keep coming from all directions. Quite soon there are just so many of them that you have to somehow try to evade them by constantly running in circles and shooting. I recall I was mostly using that green raygun and the minigun in that scene. I couldn't find a suitable youtube video of that, but I am sure there is such.

The cannon weapon was great in the next scene (after the main baddie makes an entrance), when there are so many bulls and red mechs beelining at you.

EDIT: Here I think: https://www.youtube.com/watch?v=AvOOyXdxqRM

(albeit that is in normal difficulty, maybe there were more enemies in higher difficulties?)

Canon is great for anything big in your way - be it a mecha or horde of rocketiers.
Still, grenade launcher is made exactly to clean the kleer. But it requires some timing skills.

bunching up beheadeds and then killing them all with 1 shotgun shell

economical