How do you set up a "funnel" with upsells and downsells?

Hey, I just recently made a change that I've been talking about doing for over a year now. I took my one MASSIVE product, and turned it into 6 different smaller products, with the option to get the full thing for either $15/month or $149/lifetime...

I've been wanting to do this for a while now because it gives me the option to offer upsells. For example, maybe someone buys "product 1" for $59, and I could let them know about the $149 deal...

I'm not sure exactly how to approach this though. I figure that if someone was on my site, they would know very well about the "full access deal", because I have links pointing to it everywhere on the site. Therefore, it would just be an annoyance to "remind" them again after purchasing a product.

Also, how would I offer "downsells"? Is that some sort of a pop-up that displays after they attempt to click away from the "full access sales page" or even an individual product sales page (maybe downsell to my $19 ebook)?

The only service that I'm using right now is Memberpress, which is what I use to protect my content. There's no option to implement "one click upsells". Someone would have to fill out a full checkout/registration form twice in order to buy 2 products.

So I'm just wondering how I might go about thinking about some sort of upsell/downsell funnel.

Thanks!