I personally use a rotary processor and so have no experience with manual agitation.
Rotary processors allow savings in chemistry which are relevant if you use "one-shot" baths ("one-shot" means "at-least-two-shots-you-can-have-more-if-you-are-ready-to-accept-some-compromise-with-quality-shots). I use "one-shot" baths "only" twice.
As an example, my Jobo 1520 tank says:

Rotation: 240 ml
Inversion: 485 ml

A rotary processor will save time, hassle, and chemistry. It's April you have a lot of time to get one before your summer holidays (unless it's Easter holidays we are talking).

Although a Jobo CPP or CPA would be nice, what one really needs, I understand now, is just the "rotary" stuff. It's not hard to devise a contraption that keeps temperature fairly even for a few minutes. It's not hard to have an uniform agitation pattern but that require attention and is prone to mistakes. Machines don't lose concentration and don't make mistakes.

If you look around (e.g. on eBay) you find small "simplified" rotary processors and I think would have been equally effective than my CPP-2.

They can be quite economical. I suggest, as ever, to look eBay.de because it is a mine of occasions.

Fabrizio