Infantry Flash/Rush

Support units, yes. For Infantry Flash, slower infantry units could use it well since they won’t need the extra cooldown for themselves since they’re slow

I like strong, self sustaining units who are either not fast enough to benefit from Flash/not powerful enough to benefit from Rush themselves. I dont like to use it on dancers because once danced, the target ally can easily move out of the 2 space range.

I put Infantry Flash on my L!Ike since he doesnt mind being in the middle of the fight and would only in rare cases be able to recieve the cooldown

support characters like marth or characters that already have special cool down like B!Ike

I offered some ideas when the skill first released
https://fireemblem.gamepress.gg/q-a/who-wants-strategy-craft-infantry-rush-me

I think I change my opinion about healers being good providers if infantry flash is concerned. Infantry rush, yes, because their atk often isn't spectacular. But if they receive infantry flash support, they can now charge miracle twice as fast which makes infinite tanking relatively possible on fast healers like Maria