Shadow Infernape

Despite its relatively low Attack stat, Shadow Infernape's access to Blast Burn and Shadow Boost actually makes it a very strong Fire Type attacker, though it's also fairly frail. If you're after sheer Fire Type DPS, then you could definitely do worse than this fighting monkey.

Best PvE Offensive Moveset

• Fire Spin is the better fast move with STAB and should be paired with Blast Burn.
• Flamethrower is a downgrade, but at least it's not a legacy move. 
• Rock Smash + Close Combat makes Infernape a Fighting attacker - a poor one.
• Solar Beam and Close Combat are decent moves and are occasionally useful.

Best PvE Defensive Moveset

• Rock Smash is as damaging as Fire Spin in defense but has better counter coverage.
• Flamethrower is 2-bar and has an early damage window, therefore is more likely to hit.
• Blast Burn is somewhat easy to dodge, but being a 2-bar move lets it be used more often. 
• Close Combat hits very early and is quite hard to dodge, if it gets used at all.
• Solar Beam, despite being a good coverage move, has 1 bar and is easy to dodge.

Fire Spin is preferred for its considerably better energy gains compared to Rock Smash, though both moves offer the same STAB damage output. 

Blast Burn is a legacy move obtained during Chimchar's Community Day, and is a direct upgrade over Flamethrower in both damage output and energy cost. If you don't have the former, then the latter is still okay for providing Fire-type coverage. Close Combat is Infernape's cheapest option; it has tremendous DPE, but it must be used carefully due to its self-debuff.