Barbell/dumbbell shrugs - problem with grip strength

[Tigerboy]

On shrugs, I focus only on moving my shoulders. My arms are just there holding the bar. The bar doesn't go up and down much at all.

When I use the dumbbells, same thing, they don't move up and down much at all, as I focus on just shrugging my shoulders.

I'm up to 245 lbs on the barbell for 8 reps in this manner, and I find my grip starting to give way. Dumbbells are even more drastic. I can shrug the 100 lbs dumbbells for 15 reps, on my burnout no less, and I could go further but my grip gives out (I'm holding 200 lbs after all!). I have to put them on the floor, I don't have the control to re-rack those weights.

All of this on the 1-0-1 tempo.

People have told me that I should use lifting straps, but then I thought that compromises the grip strength I need to develop.

Should I be using the straps in this case? Other tips on how I should be doing this exercise are also welcome.