Rather than trying to memorise formulae by rote, it's better to try to understand where they come from. Look carefully at the underlying principles and try to get a real handle on what each term in the formula represents. An engineer can derive many of the formulae he/she uses, out of nowhere, by remembering how things behave.
A simplified example. Suppose I had forgotten that P=V²/R. I would say to myself, more volts across a known resistance pushes proportionately more amps through. More volts makes more power and more amps also makes more power, so V must appear on top, squared. But more resistance means less amps get through per volt, so that appears on the bottom. Presto, P=V²/R.
Once you start using something every 10 minutes of the working day, it becomes automatic and very much faster, so it's good to practice. When you see electrical stuff, apply what you know to calculate things you don't know. What's the total current used by all the lights in the supermarket? What temperature would 2.5mm² T+E reach if you powered your whole house from it? How many coulombs would have to pass through your uncle's mobility scooter motor to carry him up a 1/2 mile hill at 1 in 10 gradient?
After a while, literally, it becomes second nature. I did the last one in my head in about 30 seconds, it's somewhere between 5 & 10kC for a 24V scooter depending on weights, efficiencies, road surface etc.