On my K35, I almost never use partial flaps on take off.
However, should I want to get off the ground quickly, from a short hard surfaced runway, I lower my flaps for a four second count, then put the flap switch in neutral.
Normally when flying my K35, I apply back pressure at 70 MPH indicated and it will fly off at 80 MPH indicated.
With a four second flap extension AND an additional nose up trim of 3 degrees, I apply a bit of back pressure at 55-60 MPH indicated and it will fly off about 60 - 65 MPH indicated.
Note, should something go wrong (power loss) get the nose down quickly because you will find yourself suddenly in at power off stall in this condition.
As others have said, do not be in a hurry to get the gear or flaps up. After getting airborne, lower the nose a bit, adjust the trim if necessary, and get some airspeed, then some altitude. Then you can raise the flaps. I prefer to raise the flaps first, then the gear. When the inboard gear doors open, it creates a lot of drag.
As others have said, give yourself a lot of help and do this with a lightly loaded airplane.
I have flown my K35 out of an 1800 foot long grass strip without problems on multiple occasions. But I was always about 300 pounds below max gross weight.
Hope this helps.