The obvious resources are
In tutorial, you do only some of the problems from our discussion manual. So that's another place to look for additional practice problems (though it doesn't have solutions for them).
Less obviously, you can use the old examlets from when they were on paper. The most recent paper-based offering is here:
Notice that the old paper examlets typically consisted of two pages, one white and one colored. What you're seeing on the web pages are all versions of the white sheet in one big pdf, and all versions of the colored sheet in another big pdf. Ditto the solutions. So it's not like we used to make an individual student do (say) 8 pages worth of proofs in one examlet. However, the old paper examlets were every week and only 30 minutes long. The CBTF examlets are 50 minutes but every two weeks. So consider stacking up the four sheets from two old paper examlets.
To find similar examlet pages for earlier terms, start with the first of the pages above and edit the URL. The abbreviation for the term is "su" or "fa" or "sp" followed by the 4-digit year. Be aware that some of the B lectures taught the course in somewhat different ways, so their posted exams are less comparable. Pick the old examlets (or portions of them) whose topics match what you're currently studying.
Many proofs use a standard outline. When you look at a model solution for a particular problem, try to extract its main outline (e.g. highlight the key steps). Memorizing individual proofs should not be necessary and tends to get in the way of understanding. You're likely to produce entirely wrong answers if you misidentify the problem or encounter a new problem. However, memorizing common outlines can be very helpful.