White pines don't back bud on bare stems - only fasicular buds (at the base of needle clusters). IOW, you will never have foliage where there isn't foliage now. Thus, IMHO, the game is visual foreshortening (bending to make stems appear to be shorter) and grafting.
The first thought that I have is that it may still be possible to bend the trunk between the ground and the first branch(es) so that it will appear shorter (i.e., the first branches will sit closer to ground level) - a corkscrew-ish shape. My second thought is that you'll likely end up having to graft anyway. My remaining quick thought is that life might be more enjoyable if you put it in a pond basket - they are slow growing trees in the ground, in pots. Lastly, keep that foliage near the crotch of the branches alive - don't let it get shaded out - it is likely the heart of your future bonsai, shohin or not.