The following order is recemended so you have an easier time playing.
Sheep Man (Cyber Computer)
Sheep Man weakness is Rebound Striker but if he is your first boss, buster him until he turns into the clouds. Then go somewhere where the 4 clouds aren't above you. Repeat this until he is easily defeated. You will get the Thunder Wool and you have defeated Sheep Man.
In Normal Mode, two spark balls shoot out of him just before he turns into the cloud, and when his clouds shoot sparks the first 3 clouds will spread sparks on the ground and the fourth cloud will also spread sparks but also shot spark balls on each side.
Not really much difference of Normal, Except sparks can come from Sheep Man's feet when he lands.
Use the same strategy as with Mega Man. Protoman can block Sheep Man electric balls with the Proto Shield.
You can defeat Sheep Man easier using Bass just buster him and when he turns into the clouds shoot diagonally.
Pump Man (Sewers)
Pump Man will create his own pump-like "Leaf Shield" with 4 water balls. Then, a minute after that, He will shoot the four balls airborne in four diagonal directions. Use the Thunder Wool until there's none left. Then buster him whenever Pump Man doesn't have the four balls circling around him. You will get the Water Shield.
Pump Man can now create more water balls. And after he's done pumping he may throw a pump handle boomerang towards your character. When he gets it back, blast him quickly. He will jump towards the room, after the 2nd or 3rd jump, he will release the Water Shield. Getting away from being cornered is the best way to evade.
Solar Man (Solar Power Plant)
Solar Man starts with an small fireball, And it has a small damage. Firing a buster on the his fireball above him may enlarge it, Making his attack more powerful. His attack is jumping and throwing down a fireball onto the floor. When the fireball reaches the floor, it splits, making two fireball blazes that go horizontally. Also Water Shield can make his fireball small. Making it a short and easy battle.
Chill Man (Arctic Mountains)
Nitro Man (Highway)
Nitro man throws Wheel cutters which move on the floor and goes up walls.(you can use chill spike, but they can easily be jumped over). When he turns into motorcycle mode, place a chill spike on the ground so he'll run over it and take damage. When he comes at you jump over him. Repeat until he dies.