Shower control problems

I have two problems:

One is a Grohe shower only control. It has a lever handle behind the knob handle it is close to the escutcheon. The front handle is a round knob type control. Both controls function as designed except for one thing the lever handle that controls the volume of water is very hard to turn. This is a shower that doesn’t get much use so I am thinking that disassembling, cleaning and lubing with white grease might do the trick.
The only thing that gives me caution is the last time I tried to fix a small drip in a Grohe Tub/Shower Control I embarrassed myself in front of the customer by not being able to take the darn thing apart.

Number two is more mundane a Delta shower only control. Me thinks it is a 1300 series. The hot water takes an unusually long time to come up compared to the nearby sink and the flow is very low. I still have to see if it’s the fancy one with temp and pressure or just the plain vanilla one however changing the cartridge should do the trick, yes??

I'd use the silicone plumber's grease rather than white lithium (but then again, I'm not a pro). If you know the model number, Grohe has parts breakdowns on their website. Is that grease listed for use on a potable water system?

You never wnat the customer around when taking apart a Grohe valve. Some times you "gotta do what you gotta do" to get them apart.