I use very small nails to hold the sheer strip in place as well as any other strips that can't be held in place with clamps and masking tape. Only a very small number of strips need a small number of nails to do the job. The nails I use are only about as thick as staples I have seen others using.

Under the head of the nail, I have a square of wood cut from waste strips. That allows some pressure on the strip with no risk of marking it and makes it easier to remove the nail.

The hole left by the nail is easily hidden with a damp cloth and a hot iron. The same method of swelling the timber to close the hole works for staples as well as long as the leg of the staple didn't tear the timber. Staples I have seen others use have a habit of sometimes tearing the timber a bit. A nail tends to just push the fibres of the timber apart without tearing.

If you are worried about having enough hands to drive the nails in, someone on this forum suggested driving the nails, complete with little square of timber, into the strip before it is placed on the forms. Then you only need one hand to drive them into the form when the strip is in place.

Most strips don't need any nails. Some designs will need more than others.

My nail holes are less visible than a lot of staple holes that I have seen.

With the right staples, the holes can probably be hidden fairly well. The same applies to nails.