Easy ways to max Strenght and Stealth skill

Stealth: Start up a contact mission that has no wanted levels(I recommend Pier Pressure), go on the pier, enter stealth and wack people from behind, each stealth takedown ups your skill by like 2%
Strength: Start up yet again any missions without wanted levels (I recommend Blow Up 3), go to the hospital on Strawberry/Davis (near impound lot), and start punching the paramedics, they'll keep spawning, 20 punches should up your skill by 1%