you will have to stabilize the strain, your thinking of making an auto strain, your first batch of seeds you will have to go through make clones, then spray clones to se on the plants.
the col silver will work and yes you can buy it but it is real easy to make. i use silver thisolate and get good results, go check out the super skunk diary. i sprayed a branch and made seed. i use photo period strains as i have more control on when things flower. so you will spray the sour diesel and use it on the ruderalis or will this be the opposite and you spray the ruderalis then get seed from the sour diesel?
making autos is hard and you may not get as many seeds as you think.
when i spray a branch i know that branch will give pollen, but it is not much pollen but i know that will make about 40 plus seed. not tons but a small handful.
you also want to make sure the ppm of the colloidal silver is higher that a .20 reading on the meter other wise the spray will be too weak.
if you have more questions let me know, i ve been spraying things for seed now for a while