I too find it easier to achieve smooth downshifts using engine/gearbox speed matching as described by Zepp and eternal05 (“slow release”), rather than by throttle blipping which, in order to achieve a smooth downshift, requires that you let out the clutch at the precise moment in the blip’s decay when engine and gearbox speeds match.
Note that when Zepp says “roll on the throttle” (with the clutch held in), it’s usually a fairly slight roll-on (i.e. don’t “grab a handfull”). You’re trying to match engine revs (using the throttle) with the new speed of the gearbox (in the lower gear). If you do it well enough, when you let out the clutch (smoothly), the bike will neither speed-up nor slow down.
That said though, with enough practice, I’m sure that the blip technique soon becomes second nature, so whatever floats your boat…