I’m currently using both bands and chains in my training.
Bands on Deadlifts only.
Chains on Squats and Bench.
How ever you put it together, make sure to keep the reps low (2-4 range) b/c the stress on your joints in wicked high with these additions.
I typically work up to a prescribed weight with my three lifts, then strip off some weight and do a few speed sets after I hit the heavy number I wanted to that day.
The one time I have had to ‘jerry-rig’ bands for deadlifts, this is what I did.
Using long bands btw.
Using the bottom of the rack, I slid it under between the metal and the floor and then looped it back into itself. This puts all the tension (depending on your height) at the top which will work out well for you b/c that’s where you said you were weak.
If you are 6 weeks out, I’d say hit it hard with these tools for the next 3 weeks, then taper off your assitance work and lose the bands/chains and focus on form and speed.