Sitting on a firm surface, use a ball in circular motions to massage the quadriceps area.
To add extra pressure, place one hand on top of the other and lean forward to use your bodyweight.
Work the whole area, bottom of the thigh by the knee all the way towards the hip.
You can also work on the outside of the thigh by pulling the ball into the thigh, and on the inside of the thing by pushing the ball outwards. Whilst doing this you can also bend and straighten the knee.
An alternative is to use a pole, rolling pin or massage stick. Starting at the bottom of the thigh, roll up and down a couple of inches.
Roll inside and outside the thigh. If you find a tender spot or area of restriction then a) move the stick side to side so that you roll over the muscle and/or b) bend and straighten the knee.
Then move up a couple more inches and repeat the process until you cove the whole quad area.
You are in charge of the pressure. It is not necessary to 'smash' the muscles. Getting even a little pressure with movement is beneficial. It may be uncomfortable but it should NEVER be painful. Little and often is best but especially before activity and after periods of inactivity.