I bought five identical bathroom scales from Amazon. I weighted myself on each one repeatedly to confirm that they were repeatable and reported consistent weights, and did the same against my scale at home for a sanity check.
I then leveled the aircraft by jacking up various places and sliding sheets of thin plywood under each wheel until it was level in both axes.
I then jacked up each wheel and slid the scales under. I put one scale under the nose wheel and two under each main gear, with a sturdy piece of wood to spread the load across the two scales under each main gear.
My scales only showed their values for a minute or less before going blank, so once I was all set, I jacked a wheel up to take the weight off the scale and then lowered it back on to get a reading. I did this a few times for each wheel and confirmed I got consistent totals on each wheel.
Later I added a weighted crush plate behind the prop and reweighed out of paranoia. I was pleased to find the results measured on another day aligned well with my calculations.
As long as you are comfortable with the math of weights, arms, and moments (multiply and add), there's no need to have a special W&B form. My DAR accepted a piece of paper showing the measurements and calculations. If you aren't comfortable, figure it out or get help because this could kill you if you do it wrong.
David