It has to be difficult for your father to have you see him in such a vulnerable position. This kind of situation comes up whenever an adult child is caring
for a parent, but it's hardest when you're caring for a parent of the opposite sex.
You can make it easier on your dad by letting him take the lead and encouraging him to do as much for himself as possible. Respect his dignity and autonomy by approaching each task with a question: "We need to put your support hose on now. Would you like to do it or have me do it?"
Suggest that your father do as much of each task as he can: "I'll start it and you can let me know when you're ready to take over." Even when your parent really can't do much, you can speak encouragingly about the future: "I'll do it this time, and maybe you can do it next time."
Because these situations are stressful for your father (and for you), try to create a relaxing environment by putting on the radio, turning down the lights, anything that takes the focus off the two of you. Speak soothingly and encouragingly, use humor if it helps defuse the tension -- or just talk about anything other than what's going on.
Timing is important too. If your father has company for dinner, for example, wait until everyone leaves to start the bathing or bedtime routine.
Depending on your relationship with your dad, you might find it works to acknowledge the reversal in roles by reminding him -- with respect and gratitude -- of how he once did similar tasks for you. You could ask him, "What was it like when you used to give me a bath?" He may enjoy reminiscing, and by bringing it up, you send the unspoken message "I'm just returning this wonderful favor you did for me."