Why you always mention training as some factor? Pretty sure others like turks and mongols also used to have better training, equipment, tactics etc when they won battles, it's only natural.
Undisciplined tribes with no artillery and forts , equipped mostly with swords, shields and jezails were up against one best army in the region beside East India Company. The organization of Sikh army along Euopean lines was definitely a big factor in their successes against Pashtuns....bravery of Pashtuns was not working
Army of Ranjeet Singh
Ranjeet Singh organized his army on the lines of European pattern. The importance of cavalry decreased and infantry became the most important branch of the structure of the army. He engaged French and Italian officers.
Two European generals , Monsier Ventura and Monsier Allard, arrived at the court of Ranjeet Singh. Monsier Vantura was an Italian by birth , and an infantry colonel in the French service and Monsier Allard was a Frenchman who was also colonel in cavalry. Ranjeet Singh employed them to organize his army on European lines. The tomb of Anarkali was converted into a cantonment and high salaries were fixed for them (Steinberg, Henry, "The Punjab", 1846, p-98). They raised new regiments which were disciplined and drilled after the manner of European cavalry.
The third European general arrived in the court of Ranjeet Singh in 1825. It was Monsier Court who had received his training at Ploytech institution at Paris. He served Martial Bassiers in Spain as Aid-de-camp. The fourth general was Italian by birth, Monsier Avitabile , entered into the service of Ranjeet Singh.
Ranjeet Singh also extended employment to the ex-naiks and deserting sepoys and native officers of the East India Company's service.
Ranjeet Singh had a large and well-disciplined army. It consisted of thirty-one regiments of infantry , nine regiments of cavalry, the hundred and eighty eight pieces of artillery of various caliber. Nearly one-half of his regular army was commanded by the French and other European officers and the rest by his native officers.
Besides these troops, there were also forces of irregulars in his army, furnished by Jagirdars. The annual expenditure incurred by the Maharaja in the payment of his regular army was Rs.1,27,96,482.
Soldiers were armed and clothed by the state, and with the exception of two or three battalions commanded by English officers, were organized according to the French system. The men comprising the army were almost entirely Sikhs. Some European officers served in both the civil and military administration of Ranjeet Singh. General Ventura and General Avitabile held civil charges in addition to their military responsibilities. Ventura served as the governor of Multan and Avitabile held civil charges as governor of Wazirabad and later of Peshawar. Merlom, the American, was governor of Jearata and later of Gujrat. John Holmes served as the governor of Gujrat.
Ranjeet Singh payed special attention to the development of armoury of cannons. He installed factories for this purpose and engaged skillful persons in these factories till 1839. There were found hundred and seventy persons with five thousand men to operate these factories in Ranjeet Singh army, the most important among them were Ilahi Bakhsh, Ghaus Khan, Sardar Lehanah Singh etc..In March 1839, the Maharaja appointed Gnaga Ram as the paymaster of the irregular forces. In 1806 Ranjeet Singh appointed Mokham Chand , a Khatri, as the chief of his army. He served from 1806 to 1814 the year in which he died.
In addition to the regular and irregular army, the Lahore government had also on its pay a body of irregular cavalry called Akhalees. They were religious fanatics.