You're going to be barraged with all sorts of suggestions. Use this program or that method or no method. All kinds of learning models will rain down upon your query. Some valid. Some not.
Your desire for a "reliable and quick method" of getting to 25WPM+ is the same desire I have. I'm copying random characters (22wpm) at 90% accuracy and normal text (25 wpm) with 80% accuracy.
I'm using "Just Learn Morse" which will spit out a statistical analysis of your copy on completion.
The program does not lie. It does not cut you slack. It does not allow for exceptions. It will tell you exactly how many words per minute you copy and what percentage of the text you copied correctly and exactly what letters/numbers/signs you erred on and how many times. It is brutal in it's reality. Yet rewarding as you advance.
Give it a look.http://justlearnmorsecode.com/
I'll testify to this method being "reliable" as for "quick"
?.....depends on how you define it. I'm giving it 15-20 minutes a day, 5-6 days a week. (Yes, sometimes 3-4 days a week and then I notice the drop)....so the "quick" part is really up to you and your consistency.
Either way, it's fun.