Downwind in Shifts?

So I'm wondering what y'all do to spot them, the shifts I mean.

Do those electronic gizmo things come into play?

I've not felt the need for them upwind, one thing the years on the board
does gift you with is a 'feel' for wind direction, it's deadened a bit sat
down and with the infernal wiggle stick bit, but it's still there just the
same.

But down wind it's not, or at least I haven't managed to totally spot the
more subtle changes that can help. Less so in the Blaze than the Alto, I
guess without the curly whirly kite to go by and I'm not totally convinced
the Blaze makes more ground fast enough to sail high angles, I think it's
more lazer like in that regard..

So what do you single handed folk do to judge which way to go and when.

I mean it's o.k. if you get an obvious one as you round the top mark, but
further down in a long leg in puffy stuff like we've had down here of late.

Any golden rules, pointers, do the gadgets even function downhill? (Don't
really know what they do uphill, guess they are compasses of sorts).