Light screen wasn't used often, it was mostly filler. Only used it when I was sure Entei could kill the other pokemon so Pichu would do nothing if it wasn't for Light Screen. Fire types were not a problem at all lol. Non flash fire mons were just killed and flash fire pokemon were killed with HP ground or by switching in Latios, who kills those with ease. Scizor was just really cool against fires, because he delays them another turn when he protects and attracts all the fire moves. Bullet Punch also hurts a lot of flash fire pokemon (accept for heatran who is hit hard with Super Power). I'm now thinking about using Smeargle. It also has really low defenses. I will give it the same moveset as Pichu, but with Wide Guard over Light Screen. I Think it would work a bit better because Entei was almost always hit by earthquakes and rock slides. I hope I can get a bit futher.