I think non-stigmatic pollination is more interest if with plants in the same genus, but if you want between different genus you can use protoplast fusion.

It is rather difficult to emasculate or eliminate stigma for me. However, if you can do, use this method before cross pollination. Protoplast fusion may cause variegation due to pigment segregation. I still grow petal- variegated (white and reddish purple/anthocyanin) garden balsam in my house and observe variation in petal color. For the pink petal plant with green stem, I found red patch in pink petal occasionally (may be due transopon). I am glad to send you pictures as well as seed about it. Please let me see yours too. [email protected]