Alternate method I enjoy:

1. Get a mob of cheap riflemen with officers scattered throughout.
2. take two trenches in the middle, split the force between them.
3. Order the troops in the two trenches to swap places at the same time.
4. The enemy sees an empty trench and charges just as your troops refill it.
5. Advance and Repeat as needed to thin their numbers.

It can take some time, but is very satisfying to just walk into a trench the AI spent so many stars fortifying.

These are always win strategies, not sometimes win. ;)

I felt bad so here are some things:
1. Fun game breaking strategy:
Some maps have it where two trenches are right next to each other. Place a MG on the trench closer to your base. Let the enemies pile into the trench away from you. Profit.
2. Shotgunners:
The mechanic of Shotgunners shooting first has a remarkably useful property in that it can speed up games by 1000% percent. You can get sub minute victories on hard, and sub 2 minutes on Brutal. The strategy is kinda simple but has some execution hiccups; Spawn shotgunners and shotgunners only. Preferably get one more shotgunner then the enemy has troops. Rush enemy. Fall back if needed. Rinse and Repeat until have you enough men to just rush to the enemy base and 2 shot it. This should be rather simple and easy on the lower 2 difficulties.
3. TANKS
This one is very simple: Build up as few troops as possible but still survive. Then make Heavy Tanks and just spam them until you win.
I am working on finding more.

These are options however are not the best. While they may work on easier maps and difficulties, on things like brutal this is legit one of the worst possible options. The AI does not care about you. Since upgrading the HQ to max takes absolute ages the AI will just rush it forever until you die since the healing is extremely slow. There are also certain maps where Officers Snipers MGs don't work. Snipers have a quite limited use range, and MGs are only defensive positions. The second method you mentioned is okay however depending on how many troops you have produced in total it will range in usefulness.
It's a quite a good guide for new players with little knowledge of AI mechanics who only play on easier difficulties, but above medium I don't see this being rather effective, and on brutal nearly impossible.
One upside to this is both strategies work on all maps, contrary to many strategies that are completely reliant on map (Case in point the Sniper strategy for Map 8)