(sry if bad english) When staying in top,spam Q to your oponent. You don't have to worry about mana,and your live regeneration is extremely high,so don't worry if you fail atacks. It don't have the intention to kill, but the intention to push the enemy and don't let him kill minioms so don't gain gold,and keep low his live. That way he won't try to atack you directly, Leaving the space to eraly feed farming. Not a lot, but a bit. Of course if you had the chance try to kill using the ignite, and flash if you have to escape. Try to go back just to buy, use your ultimate to heal yourself. It have a extremly down cooldown,(a minute) so you can use it to don't let the enemy escape. Just Try to feed yourself the most you can, and trying that te oponen don't even farm. it's imposible that he don't gain exp, but you can make that he gains extrmely low gold.

If he jumps on you, use as fast as you can W and E. Just use R if you need to run away,heal yourself,and return fast,to teake advantage of the enormus healing.

later,when playin in team,you can try to star teamfights whith Q or hiting the and returning fast whith R (absolut not recomended)but it's better to let another start the teamfights.then,go for the other tank. Mundo have good mach-ups on almost every tank thanks to the knive. But that depends on your team and the rival team.